PELARGONIC ACID

PELARGONIC ACID = NONANOIC ACID = NONYLIC ACID = PELARGIC ACID


EC / List no.: 203-931-2
CAS no.: 112-05-0
Mol. formula: C9H18O2


Nonanoic acid (frequently referred to as pelargonic acid) is a naturally occurring carboxylic acid with a carbon chain-length of nine, belonging to the chemical class of saturated fatty acids commonly referred to as medium chain fatty acids (C8 to C12). 
Pelargonic acid is a clear, colourless liquid with a weak odour. 
Pelargonic acid (Nonanoic acid) is soluble in aqueous solutions however it can readily form esters and partially dissociate into the pelargonate anion (CH3(CH2)7COO-) and the hydronium cation (H3O+) in an aqueous solution. The molecular weight (158.24 g/mol) and octanol-water partition coefficient (3.4 logPow) of nonanoic acid suggest that dermal penetration is possible.


Nonanoic acid is a medium-chain saturated fatty acid. 
Nonanoic acid inhibits mycelial growth and spore germination in the plant pathogenic fungi M. roreri and C. perniciosa in a concentration-dependent manner.It has herbicidal activity against a variety of species, including crabgrass.
Nonanoic acid has been used as an internal standard for the quantification of free fatty acids in olive mill waste waters.
Formulations containing nonanoic acid have been used in indoor and outdoor weed control and as cleansing and emulsifying agents in cosmetics.

Pelargonic acid, also called nonanoic acid, is an organic compound with structural formula CH3(CH2)7CO2H. 
Pelargonic acid is a nine-carbon fatty acid. Nonanoic acid is a colorless oily liquid with an unpleasant, rancid odor. 
Pelargonic acid is nearly insoluble in water, but very soluble in organic solvents. 
The esters and salts of pelargonic acid are called pelargonates or nonanoates.

Pelargonic acid is used in herbicide formulations and in the preparation of plasticizers, resins, lubricants, and lacquers

Pelargonic acid or Nonanoic Acid is a C9 straight-chain saturated fatty acid which occurs naturally as esters of the oil of pelargonium. 
Pelargonic acid has antifungal properties, and is also used as a herbicide as well as in the preparation of plasticisers and lacquers.

Nonanoic Acid is a naturally-occurring saturated fatty acid with nine carbon atoms. The ammonium salt form of nonanoic acid is used as an herbicide. 
Nonanoic Acid works by stripping the waxy cuticle of the plant, causing cell disruption, cell leakage, and death by desiccation.

Nonanoic acid is a C9 straight-chain saturated fatty acid which occurs naturally as esters of the oil of pelargonium. 
Nonanoic acid has antifungal properties, and is also used as a herbicide as well as in the preparation of plasticisers and lacquers. 
Nonanoic acid has a role as an antifeedant, a plant metabolite, a Daphnia magna metabolite and an algal metabolite. 
Nonanoic acid is a straight-chain saturated fatty acid and a medium-chain fatty acid. It is a conjugate acid of a nonanoate. Nonanoic acid derives from a hydride of a nonane.

Nonanoic acid (Pelargonic acid, Nonoic acid) is a naturally occurring fatty acid found in both vegetable and animal fats.
Nonanoic acid (NNA) is a medium chain fatty acid, and is a naturally occurring carboxylic acid with a carbon chain length of nine. 
Nonanoic acid is used in agricultural and veterinary (AgVet) chemical products as an herbicide, and may have other uses in therapeutic goods or fragrances.

Nonanoic acid has been used in a range of agricultural chemicals as an herbicide, both in combination with other actives (particularly glyphosate), but also as a stand-alone active constituent. 
Commercial products are available with high concentrations of Nonanoic acid. Nonanoic acid is available as products for use in the home garden, both in ready to use formulations and also as concentrated formulations which require dilution prior to use.

Pelargonic acid, also known as nonanoic acid or pelargon, belongs to the class of organic compounds known as medium-chain fatty acids. 
These are fatty acids with an aliphatic tail that contains between 4 and 12 carbon atoms. 
Pelargonic acid is an oily liquid with an unpleasant, rancid odor. 
It is a very hydrophobic molecule, practically insoluble in water but very soluble in organic solvents. 
The biosynthesis of fatty acid occurs through the acetate pathway and the process is catalyzed by the Fatty Acid Synthase (FAS) enzymes. 
Structurally, FAS varies significantly across different organisms but essentially, they all perform the same task using the same mechanisms. 
Nonanoic acid is also used in the preparation of plasticizers and lacquers. Synthetic esters of nonanoic acid, such as methyl nonanoate, are used as flavorings. 
The derivative 4-nonanoylmorpholine is an ingredient in some pepper sprays. The ammonium salt of nonanoic acid, ammonium nonanoate, is an herbicide. 
It is commonly used in conjunction with glyphosate, a non-selective herbicide, to control weeds in turfgrass. 

Pelargonic acid is a clear to yellowish oily liquid. It is insoluble in water but soluble in ether, alcohol and organic solvents. 
The molecules of most natural fatty acids have an even number of carbon chains due to the linkage together by ester units. 
Analogous compounds of odd numbers carbon chain fatty acids are supplemented synthetically. 
Pelargonic acid, C-9 odd numbers carbon chain fatty acid, is relatively high cost fatty acid. 
Pelargonic acid can be prepared by ozonolysis which uses ozone is to cleave the alkene bonds. 
Example of ozonolysis in commerce is the production of odd carbon number carboxylic acids such as azelaic acid and pelargonic acid and simple carboxylic acids such as formic acid and oxalic acid.
Pelargonic acid forms esters with alcohols to be used as plasticizers and lubricating oils. 
It is used in modifying alkyd resins to prevent discolor and to keep flexibility and resistance to aging since saturated pelargonic acid will not be oxidized. 
Metallic soaps (barium and cadmium) and other inorganic salts used as a stabilizer. 
It is also used as a chemical intermediate for synthetic flavors, cosmetics, pharmaceuticals and corrosion inhibitors. 
It is known that C8 - C12 straight and saturated chain fatty acids are capable of removing the waxy cuticle of the broadleaf or weed, resulting in causing the tissue death. T
hey are used as active ingredient of environment friendly and quick effect herbicides. Pelargonic acid is the strongest one.


Nonanoic acid may be used to treat seizures (PMID 23177536).


Other names: n-Nonanoic acid; n-Nonoic acid; n-Nonylic acid; Nonoic acid; Nonylic acid; Pelargic acid; Pelargonic acid; 1-Octanecarboxylic acid; Cirrasol 185a; Emfac 1202; Hexacid C-9; Pelargon; Emery 1203; 1-Nonanoic acid; NSC 62787; n-Pelargonic acid; Emery 1202 (Salt/Mix)


IUPAC Name: nonanoic acid

Synonyms:      
1-nonanoic acid    
1-octanecarboxylic acid    
CH3‒[CH2]7‒COOH    IUPAC
n-nonanoic acid    
n-nonanoic acid    
Nonanoate    
Nonanoic acid    
Nonansäure Deutsch    
nonoic acid    
nonylic acid    
pelargic acid    
pelargon    
Pelargonic acid    
Pelargonsäure Deutsch    
pergonic acid

nonanoic acid has parent hydride nonane 
nonanoic acid has role Daphnia magna metabolite 
nonanoic acid has role algal metabolite 
nonanoic acid has role antifeedant 
nonanoic acid has role plant metabolite
nonanoic acid is a medium-chain fatty acid 
nonanoic acid is a straight-chain saturated fatty acid 
nonanoic acid is conjugate acid of nonanoate 

SYNONYMS :

NONANOIC ACID
Pelargonic acid
112-05-0
n-Nonanoic acid
Nonoic acid
Nonylic acid
Pelargic acid
n-Nonylic acid
n-Nonoic acid
1-Octanecarboxylic acid
Pelargon
Cirrasol 185A
Hexacid C-9
Emfac 1202
1-nonanoic acid
Fatty acids, C6-12
Fatty acids, C8-10
Nonansaeure
Pelargonsaeure
pergonic acid
MFCD00004433
nonoate
NSC 62787
UNII-97SEH7577T
68937-75-7
CH3-[CH2]7-COOH
CHEBI:29019
97SEH7577T
pergonate
n-nonanoate
1-nonanoate
C9:0
octan-1 carboxylic acid
1-octanecarboxylate
n-Nonanoic acid, 97%
DSSTox_CID_1641
DSSTox_RID_76255
DSSTox_GSID_21641
Pelargon [Russian]
1-Octanecarboxyic acid
CAS-112-05-0
FEMA No. 2784
HSDB 5554
EINECS 203-931-2
EPA Pesticide Chemical Code 217500
BRN 1752351
n-Pelargonate
AI3-04164
n-Nonylate
Perlargonic acid
n-Nonoate
n-pelargonic acid
KNA
EINECS 273-086-2
Nonanoic Acid Anion
Acid C9
Caprylic-Capric Acid
Nonanoic acid, 96%
3sz1
Emery's L-114
Pelargonic Acid 1202
Emery 1202
Emery 1203
octane-1-carboxylic acid

Preparation, occurrence, and uses
Pelargonic acid occurs naturally as esters in the oil of pelargonium. 
Together with azelaic acid, it is produced industrially by ozonolysis of oleic acid.

H17C8CH=CHC7H14CO2H + 4O → HO2CC7H14CO2H + H17C8CO2H
Synthetic esters of pelargonic acid, such as methyl pelargonate, are used as flavorings. 
Pelargonic acid is also used in the preparation of plasticizers and lacquers. 
The derivative 4-nonanoylmorpholine is an ingredient in some pepper sprays. 
The ammonium salt of pelargonic acid, ammonium pelargonate, is an herbicide. 
It is commonly used in conjunction with glyphosate, a non-selective herbicide, for a quick burn-down effect in the control of weeds in turfgrass.

Pharmacological effects
Pelargonic acid may be more potent than valproic acid in treating seizures.
Moreover, in contrast to valproic acid, pelargonic acid exhibited no effect on HDAC inhibition, suggesting that it is unlikely to show HDAC inhibition-related teratogenicity.

IUPAC name: Nonanoic acid
Other names: Nonoic acid; Nonylic acid;
1-Octanecarboxylic acid;
C9:0 (Lipid numbers)

Identifiers
CAS Number: 112-05-0 
EC Number: 203-931-2

Properties
Chemical formula: C9H18O2
Molar mass: 158.241 g·mol−1
Appearance: Clear to yellowish oily liquid
Density: 0.900 g/cm3
Melting point: 12.5 °C (54.5 °F; 285.6 K)
Boiling point: 254 °C (489 °F; 527 K)
Critical point (T, P): 439 °C (712 K), 2.35 MPa
Solubility in water: 0.3 g/L
Acidity (pKa): 4.96
1.055 at 2.06 to 2.63 K (−271.09 to −270.52 °C; −455.96 to −454.94 °F)
1.53 at −191 °C (−311.8 °F; 82.1 K)
Refractive index (nD): 1.4322

Hazards
Main hazards: Corrosive (C)
R-phrases (outdated): R34
S-phrases (outdated): (S1/2) S26 S28 S36/37/39 S45


Flash point: 114 °C (237 °F; 387 K)
Autoignition temperature: 405 °C


Categories: Alkanoic acids
Herbicides
Pelargonic Acid
Pelargonic acid is found naturally in pelargoniums and is a highly effective fatty acid widely used in the treatment of unwanted plants.

How does Pelargonic Acid work?
Pelargonic acid destroys the cell walls of the leaves of the weed. 

This results in the cells losing their structure and drying out within a short space of time, under normal conditions this will be visible within 1 day after treatment.

Only the green parts of the plant are affected by this action, the woody bark of the plant is unaffected as the cells are too stable and the active ingredient has no way of penetrating the surface. 
Therefore the product can be used under hedges, trees and bushes without fear of destroying the whole area.


Uses
Pelargonic acid occurs naturally in many plants and animals. 
Pelargonic acid is used to control the growth of weeds and as a blossom thinner for apple and pear trees. 
Pelargonic acid is also used as a food additive; as an ingredient in solutions used to commercially peel fruits and vegetables.


Pelargonic acid is present in many plants. 
Pelargonic acid is used as an herbicide to prevent growth of weeds both indoors and outdoors, and as a blossom thinner for apple and pear trees. 
The U.S. Food and Drug Administration (FDA) has approved this substance for use in food. 
No risks to humans or the environment are expected when pesticide products containing pelargonic acid are used according to the label directions. 

I. Description of the Active Ingredient Pelargonic acid is a chemical substance that is found in almost all species of animals and plants. 
Because it contains nine carbon atoms, it is also called nonanoic acid. 
It is found at low levels in many of the common foods we eat. 
It is readily broken down in the environment. 


II. Use Sites, Target Pests, And Application Methods Pelargonic acid has two distinct uses related to plants: weed killer and blossom thinner. 
[Note: The substance can also be used as a sanitizer, a use not addressed in this Fact Sheet.] 

o Weed killer Growers spray pelargonic acid on food crops and other crops to protect them against weeds. 
For food crops, pelargonic acid is allowed to be applied from planting time until 24 hours before harvest. 
The pre-harvest restriction assures that little or no residue remains on the food. 
The chemical also controls weeds at sites such as schools, golf courses, walkways, greenhouses, and various indoor sites. 

o Blossom thinner Growers use pelargonic acid to thin blossoms, a procedure that increases the quality and yield of apples and other fruit trees. 
Thinning the blossoms allows the trees to produce fruit every year instead of every other year. 


III. Assessing Risks to Human Health Pelargonic acid occurs naturally in many plants, including food plants, so most people are regularly exposed to small amounts of this chemical. 
The use of pelargonic acid as an herbicide or blossom thinner on food crops is not expected to increase human exposure or risk. 
Furthermore, tests indicate that ingesting or inhaling pelargonic acid in small amounts has no known toxic effects. 
Pelargonic acid is a skin and eye irritant, and product labels describe precautions that users should follow to prevent the products from getting in their eyes or on their skin.

THE USE OF PELARGONIC ACID AS A WEED MANAGEMENT TOOL 
Steven Savage and Paul Zomer Mycogen Corporation, San Diego, California In 1995, the Mycogen Corporation introduced Scythe®, a burn-down herbicide containing 60% of the active ingredient, pelargonic acid. 
Pelargonic acid is a naturally occurring, saturated, nine-carbon fatty acid (C9:0).

 Pelargonic acid occurs widely in nature in products such as goat's milk, apples and grapes. 

Commercially it is produced by the ozonolysis of oleic acid (C18:1) from beef tallow. 
Pelargonic acid has very low mammalian toxicity (oral, inhalation), is not mutagenic, teratogenic or sensitizing. 

It can cause eye and skin irritation and thus the formulated product carries a WARNING signal word (Category II). 

It has a benign environmental profile. As a herbicide, pelargonic acid causes extremely rapid and non-selective burn-down of green tissues. 

The rate of kill is related to temperature, but under all but the coolest conditions the treated plants begin to exhibit damage within 15-60 minutes and begin to collapse within 1-3 hours of the application. 

Pelargonic acid is not systemic and is not translocated through woody tissues. 
It is also active against mosses and other cryptograms. Pelargonic acid has no soil activity. 
As with most burn-down herbicides, pelargonic acid does not prevent re-growth from protected buds or basal meristems. 
Many annual herbaceous weeds can be killed completely while larger weeds, grasses and woody plants may re-grow. 
There are many practical applications of the rapid burn-down activity of pelargonic acid. 

It can be used for spot weeding, edging, lining, turf renewal, chemical pruning and suckering. 
It is particularly useful as a directed spray for killing annual weeds in container-grown woody ornamentals, under greenhouse benches and in other places where systemic herbicides can cause unwanted damage. 

If the spray of pelargonic acid does come in contact with some desired plants, the damage is strictly limited to those leaves which are actually sprayed. 

Pelargonic acid should be applied in at least 75 gallons/acre of total spray volume as activity declines at lower gallonages. 
Evidence from P31 NMR studies suggests that the mode of action of pelargonic acid is not based on direct damage to cell membranes. 
Pelargonic acid moves through the cuticle and cell membranes and lowers the internal pH of the plant cells. 
Over the next several minutes the pools of cellular ATP and Glucose-6-phosphate decline. 

Only later is there evidence of membrane dysfunction which eventually leads to cell leakage, collapse and desiccation of the tissue. 
This chain of cellular events appears to allow pelargonic acid to synergize the activity of certain systemic herbicides such as glyphosate. 

In general, bum-down herbicides are antagonistic to the activity of systemic herbicides, but in a tank mix pelargonic acid has been shown to allow greater and more rapid uptake of glyphosate without interfering with translocation. 
This type of synergy is completely distinct from the enhancement seen with various surfactants used as adjuvants or formulation components for glyphosate. 

By using high volume applications of a tank mix it is possible to combine the rapid kill of pelargonic acid with the systemic action of glyphosate. 

At low application volumes (e.g. 20-30 GPA), pelargonic acid still enhances glyphosate uptake and improves its overall performance, but there is no immediate burn of the treated foliage. 

Scythe herbicide was registered for non-crop use in 1995 and a crop registration is expected in 1996. 
This commercial formulation of pelargonic acid has a wide range of weed control applications both as a contact, non-selective agent and as a tank mixing partner with systemic herbicides such as glyphosate.

The Herbicidal Potential of Different Pelargonic Acid Products and Essential Oils against Several Important Weed Species 
Ilias Travlos 1,* , Eleni Rapti 1 , Ioannis Gazoulis 1 , Panagiotis Kanatas 2 , Alexandros Tataridas 1 , Ioanna Kakabouki 1 and Panayiota Papastylianou 1 1 
Laboratory of Agronomy, Department of Crop Science, Agricultural University of Athens, 75 Iera Odos str., 118 55 Athens, Greece; 

Published: 30 October 2020             

Abstract: There is growing consideration among farmers and researchers regarding the development of natural herbicides providing sufficient levels of weed control. 
The aim of the present study was to compare the efficacy of four different pelargonic acid products, three essential oils and two natural products’ mixtures against L. rigidum Gaud., A. sterilis L. and G. aparine L. Regarding grass weeds, it was noticed at 7 days after treatment that PA3 treatment (pelargonic acid 3.102% w/v + maleic hydrazide 0.459% w/v) was the least efficient treatment against L. rigidum and A. sterilis. The mixture of lemongrass oil and pelargonic acid resulted in 77% lower dry weight for L. rigidum in comparison to the control. Biomass reduction reached the level of 90% as compared to the control in the case of manuka oil and the efficacy of manuka oil and pelargonic acid mixture was similar. 
For sterile oat, weed biomass was recorded between 31% and 33% of the control for lemongrass oil, pine oil, PA1 (pelargonic acid 18.67% + maleic hydrazide 3%) and PA4 (pelargonic acid 18.67%) treatments. In addition, the mixture of manuka oil and pelargonic acid reduced weed biomass by 96% as compared to the control. 
Regarding the broadleaf species G. aparine, PA4 and PA1 treatments provided a 96–97% dry weight reduction compared to the corresponding value recorded for the untreated plants. 

PA2 (pelargonic acid 50% w/v) treatment and the mixture of manuka oil and pelargonic acid completely eliminated cleaver plants. 
The observations made for weed dry weight on the species level were similar to those made regarding plant height values recorded for each species. 

Further research is needed to study more natural substances and optimize the use of natural herbicides as well as natural herbicides’ mixtures in weed management strategies under different soil and climatic conditions. Keywords: bioherbicide; pelargonic acid; manuka oil; lemongrass oil; pine oil; grass weeds; broadleaf weeds 1. 
Introduction Weeds are considered to be one of the major threats to agricultural production since they affect the crop production indirectly, by competing with the crop for natural resources, sheltering crop pests, reducing crop yields and quality, and subsequently increasing the cost of processing [1]. Chemical control remains the most common control practice for weed management. Unfortunately, this overreliance on herbicides has led to serious problems, such as the possible injury to non-target vegetation and crops, the existence of herbicide residues in the water and the soil and concerns for human health and safety [2–5]. 
Another major issue associated with the use of synthetic herbicide is Agronomy 2020, 10, 1687; doi:10.3390/agronomy10111687 www.mdpi.com/journal/agronomy Agronomy 2020, 10, 1687 2 of 13 the growing problem of herbicide resistance since many harmful weed species including Amaranthus, Conyza, Echinochloa, and Lolium spp. are notorious for their ability to rapidly evolve resistance to a wide range of herbicide sites of action. 
The development of natural herbicides based on either organic acids or essential oils could decrease these negative impacts. 
They are less persistent in comparison to synthetic herbicides, more environmentally friendly, and they also have different modes of action which can prevent the development of herbicide-resistant weed biotypes [7,8]. Organic acids, essential oils, crude botanical products and other natural substances derived from plant tissues can be used as bio-herbicides in terms of weed management in both organic and sustainable agriculture systems [9]. 
Such natural substances face several opponents among the European Commission members, since there are doubts regarding the registration processes of natural products due to the lack of relevant toxicological data for their use at commercial scale [10]. Although these concerns might exist, there is evidence that most essential oils and their main compounds are not necessarily genotoxic or harmful to human health [11]. Such natural herbicides are sometimes less hazardous for environmental and human health in comparison to the commercial synthetic herbicides. 
In the case of pelargonic acid, toxicity tests on non-target organisms, such as birds, fish, and honeybees, revealed little or no toxicity. 
The chemical decomposes rapidly in both land and water environments, so it does not accumulate. 
To minimize drift and potential harm to non-target plants, users are required to take precautions such as avoiding windy days and using large spray droplets. 
However, product labels describe precautions that users should follow to prevent the products from getting in their eyes or on their skin since the acid is a skin and eye irritant [13]. 
Pelargonic acid (PA) (CH3(CH2)7CO2H, n-nonanoic acid) is a saturated, nine-carbon fatty acid (C9:0) naturally occurring as esters in the essential oil of Pelargonium spp. And can be derived from the tissues of various plant species [14–16]. Pelargonic acid along with its salts and formulated with emulsifiers is used in terms of weed management as a nonselective herbicide suitable either for garden or professional uses worldwide [8,14]. 
They are applied as contact burndown herbicides, which attack cell membranes and then as a result, cell leakage is caused and followed by membrane acyl lipids breakdown . 

The phytotoxic effects due to the application of pelargonic acid are visible in a very short time after spraying and the symptoms involve phytotoxicity for the plants and their cells, which rapidly begin to oxidize, and necrotic lesions are observed on the aerial parts of plants [18]. 
The potential use of pelargonic acid as a bioherbicide poses an attractive non-chemical weed control option which can be effectively integrated with other eco-friendly weed management strategies in important crops such as soybean [19]. Several commercial pelargonic acid-based natural herbicides include also maleic hydrazide (1,2-dihydro-3,6-pyridazinedione) which is a systemic plant growth regulator that has also been used as a herbicide since its introduction [20]. 

Maleic hydrazide (1, 2-dihydropyridazine-3, 6-dione), a hormone-like substance synthesized and first introduced to USA in 1949, with crystal structure and structural similarity to the pyrimidine base uracil [20–22]. 
After application to foliage, maleic hydrazide is translocated in the meristematic tissues, with mobility in both phloem and xylem. 
Although its mode of action is not clear, it can be used effectively for sprout suppression on vegetable crops such as onions and carrots as well as for the control of troublesome parasitic weed species where synthetic herbicides are limited [24–26]. Essential oils derived from a variety of aromatic, biomass, invasive or food crop plants are also known to have potential as natural non-selective herbicides [9,27–29]. 

Similarly, with the case of pelargonic acid, the foliage of weeds burns down in a very short time after application, which is more effective against young plants than older ones [30]. 
Manuka oil is isolated from the leaves of Leptospermum scoparium J. R. Forst. and G. Forst. and is considered to be an acceptable product in terms of organic standards [9]. 
The active ingredient in this essential oil is leptospermone, a natural b-triketone, which targets the enzyme p-hydroxyphenylpyruvate dioxygenase (HPPD) such as the conventional synthetic herbicides mesotrione and sulcotrione [31–33]. Lemongrass essential oil, derived from either Cymbopogon citratus Stapf. or C. flexuosus D.C. containing up to 80% citral is also commercialized Agronomy 2020, 10, 1687 3 of 13 as an organic herbicide whose mode of action involves the disruption of polymerization of plant microtubules [34]. 

Lemongrass oil acts as a contact herbicide, and since the active ingredient does not translocate, only the portions of plants receiving the spray solution are affected. 

Pine essential oil is also commercialized as a 10% aqueous emulsion for weed control as a natural herbicide. 

It is derived from steam distillation of needles, twigs and cones of Pinus sylvestris L. and a wide range of other species belonging to Pinus spp. and includes terpene alcohols and saponified fatty acids. Monoterpenes such as a- and b-pinene can increase the concentration of malondialdehyde, proline and hydrogen peroxide, indicating lipid peroxidation and induction of oxidative stress in weeds [35,36]. 
The aim of the present study was to evaluate and compare the efficacy of four different pelargonic acid products, three essential oils and two mixtures (of a pelargonic acid product and two essential oils) against three target weed species, i.e., rigid ryegrass (Lolium rigidum Gaud.), sterile oat (Avena sterilis L.) and cleaver (Galium aparine L.). 

2. Materials and Methods 2.1. Plant Material Collection and Seed Pretreatment Seeds of rigid ryegrass (L. rigidum), sterile oat (A. sterilis) and cleaver (G. aparine) were collected from winter wheat fields of the origins of Fthiotida, Viotia and Larisa, respectively, during June 2019 (Table 1). 
In each field, panicles and seeds were collected from 20 plants and transferred to the Laboratory of Agronomy (Agricultural University of Athens). 
Table 1. Weed species studied, origins and geographical positions where seed collection was carried out. Common Name Scientific Name Origin Position Rigid ryegrass Lolium rigidum Gaud. Fthiotida 39◦08007” N, 22◦24056” E Sterile oat Avena sterilis L. Viotia 38◦24041” N, 23◦00040” E Cleaver Galium aparine L. Larisa 39◦25051” N, 22◦45047” E Two experiments were conducted and repeated twice to evaluate and compare the efficacy of the different pelargonic acid products, essential oils and mixtures of natural herbicides against the three target weed species. 
The collected seeds were air-dried, threshed, placed in paper bags, and stored at room temperature to be used in the subsequent experimental runs. 
Different were the seed pretreatment processes carried out to release dormancy in the seeds of the grasses and in the seeds of cleaver. 

To release dormancy in the seeds of rigid ryegrass and sterile oat, the seeds were individually nicked with 2 teeth tweezers and placed in Petri dishes on two sheets of Whatman No.1 paper filter disk (Whatman Ltd., Maidstone, England) saturated with 6 mL distilled water, in 10 November. The Petri dishes were kept at 2–4 ◦C (refrigerator) for a period of 7 days. After that, the non-dormant seeds were used for sowing during the first experimental run, carried out during 2019. About half of the total collected grass weed seeds had been stored at room temperature to be used in the second experimental run, carried out during 2020. For cleaver, the seeds were sown in rectangular pots (28 × 30 × 70 cm3 ) and buried into the soil at approximately 3–4 cm depth, in 17 June. The pots were kept outside under natural conditions for 3 months to break the dormancy in the cleaver seeds. 
The seeds were carefully removed from the pots in 19 September. 
Afterwards, they were air-dried, placed and stored in paper bags at room temperature until use either for the first or the second experimental run. 
Approximately fifteen seeds of rigid ryegrass and sterile oat, and twenty seeds of cleaver were sown in separate pots (12 × 13 × 15 cm3 ) in 18 November 2019, during the experiments of the first run. Rigid ryegrass and sterile oat seeds were sown at 1 cm depth. 
Cleaver seeds were also sown at 1 cm depth to achieve maximum seedling emergence. 
Pots had been filled with a mix of herbicide–free soil from the experimental field of the Agricultural University of Athens and peat at the ratio of 1:1 (v/v). 
The soil of the experimental field is clay loam (CL) with pH value of 7.29, whereas the contents of CaCO3 and organic matter were 15.99% and 2.37%, respectively. 
Moreover, the concentrations of NO3 − Agronomy 2020, 10, 1687 4 of 13 P (Olsen) and Na+ were 104.3, 9.95 and 110 ppm, respectively. 
When the weed seedlings of all the weed species reached the appropriate phenological stage for spraying, they were carefully thinned to twelve plants per pot. 
All pots were watered as needed and placed outdoors. The pots were randomized every 5 days in order to achieve uniform growth conditions for all the plants. 
Regarding the duration of the first experiment, it was conducted between 18 November and 28 December 2019. 

Regarding the second experimental run, the pot experiments were established in 14 January 2020 and were conducted until 25 February 2020. 

For the second experimental run, the same courses of action were carried out regarding seed pretreatment and experiment establishment as compared to the corresponding ones carried out for the run. Typical climatic conditions for Greece were observed during the experimental periods. 
Maximum month temperatures for November, December, January and February were 21.3, 15.6, 9.2 and 11.3 ◦C, respectively. 
Minimum month temperatures for the same months were 14.2, 9.2, 2.1 and 1.8 ◦C, respectively, whereas total heights of precipitation for these months were 120.4, 90.6, 16.4 and 12.0 mm, respectively. 2.2. Experimental Treatments Several pelargonic acid products along with essential oils with a potential herbicidal action have been used. In particular, PA1 (3Stunden Bio-Unkrautfrei, Bayer Garten, Germany) and PA2 (Beloukha Garden, Belchim Crop Protection NV/SA, Technologielaan 7, 1840 Londerzeel, Belgium) contained only pelargonic acid at concentrations shown in Table 2, while PA3 and PA4 (Finalsan Ultima, W. Neudorff GmbH KG, Emmerthal, Germany) contained pelargonic acid along with maleic hydrazide (Table 2). For PA1, PA2, PA3 and PA4 treatments, pelargonic acid was applied as a single treatment without being mixed. Regarding the treatments containing essential oil application, EO1 (Manuka oil, Leptospermum scoparium, Salvia, India), EO2 (Lemon grass oil, Cymbopogon citratus, Sheer Essence, India) and EO3 (Pine oil, Pinus sylvestris, Sheer Essence, India) were used at 5% concentration. 
All of the essential oils were diluted with water before treatment to achieve a 5% concentration. 
In fact, commercial essential oils must be applied at high concentrations, often 10% or more per volume [30]. 

In the present study, an intermediate concentration of 5% was selected to reduce the cost of essential oil application in order to evaluate whether sufficient weed control can be achieved with the application of such natural herbicides at lower concentrations, acceptable also by an economic aspect. All herbicide applications were carried out with a handy pressure sprayer equipped with a variable conical nozzle. 

Spraying was carried out at 0.3 MPa pressure and the spraying angle was 80◦ . 
The height between the conical nozzle and the soil level was 40 cm for all the experimental treatments. 
The spray head was set to move over the plants at 1.5 km h−1 and the apparatus was calibrated to deliver the equivalent of 200 L ha−1 . 
The treatments were applied in 20 December, 2019, for the two runs of the first year (in 16 February 2020, for the two runs of the second year) when plants had reached the phenological stage of 2–3 true leaves, corresponding to stage 12–13 of the BBCH scale for rigid ryegrass and sterile oat, and the phenological stage of 3–4 true leaves, corresponding to stage 13–14 of the BBCH scale for cleaver. The pots were placed outdoors, and the leaves of the weed plants were vertically oriented at the time of spraying. 

The experimental treatments were carried out at a sunny day and air temperature during spraying was 16.1 ◦C, for the first year (13.4 ◦C for the second year). 

Table 2. The experimental treatments (e.g., natural herbicides) applied in the current study. 
Treatment Active Ingredient Content in (g/L) or (mL/L) Dose Rate (L/ha) Active Ingredient per Unit Area in (g/ha) or (mL/ha) Abbreviation Control - - - - 
Pelargonic acid 18.67% 18.67 1 200 3734 3 PA1 Pelargonic acid 50% 50 1 200 10000 3 PA2 Pelargonic acid 3.102% + maleic hydrazide 0.459% 3.102 1 200 620.4 3 PA3 Pelargonic acid 18.67% + maleic hydrazide 3% 18.67 1 + 3 1 200 3734 3 + 600 3 PA4 Agronomy 2020, 10, 1687 5 of 13 

Table 2. Cont. Treatment Active Ingredient Content in (g/L) or (mL/L) Dose Rate (L/ha) Active Ingredient per Unit Area in (g/ha) or (mL/ha) Abbreviation Manuka oil 5% 5 2 200 1000 4 EO1 Lemongrass oil 5% 5 2 200 1000 4 EO2 Pine oil 5% 5 2 200 1000 4 EO3 Pelargonic acid 18.67% + maleic hydrazide 3% + Manuka oil 5% 18.67 1 + 3 1 + 5 2 200 3734 3 + 600 3 + 1000 4 M1 Pelargonic acid 18.67% + maleic hydrazide 3% + Lemongrass oil 5% 18.67 1 + 3 1 + 5 2 200 3734 3 + 600 3 + 1000 4 M2 1 Data refer to the active ingredient contents of the four different pelargonic acid formulations. The active ingredients are expressed in g/L. 2 
Data refer to the active ingredient contents of the three different essential oil formulations. 
The active ingredients are expressed in mL/L. 3 Data refer to the amount of the active ingredient of the four different pelargonic acid formulations per unit area. 
The amounts are expressed in g/ha. 4 Data refer to the amount of the active ingredient of the three different essential oil formulations. 
The amounts are expressed in mL/ha. 

2.3. Evaluation of the Efficacy of Each Natural Herbicide against Targeted Weeds To evaluate the efficacy of each natural herbicide against the targeted weed species, dry weight and plant height of four plants per pot were measured for each weed species at 1, 3 and 7 days after treatment (DAT). 
For measuring dry weight, the selected plants were dried at 60 ◦C for 48 h and then the measurements of dry weight were carried out. 
The scale to measure dry weight had an accuracy of three decimal places and plant height was measured to nearest cm. 
Each one of the experiments started with twelve plants in each pot and four plants were removed from each pot at 1, 3 and 7 DAT. 
The assessment period was not longer than 7 DAT because the current experiment was focused on evaluating the knockdown effect of the natural herbicides on each one of the studied weed species. No observations regarding necrosis levels or NDVI values were made since these will be the objects of future experimentation. 2.4. Statistical Analysis Both of the experiments were repeated twice per year. 
All the experiments were conducted in a completely randomized design with four replicates and nine experimental treatments (PA1, PA2, PA3, PA4, EO1, EO2, EO3, M1 and M2). 

Four replicate pots were used for the evaluation of the effects of the experimental treatments on each weed species. 
For all the experiments, the weed dry weight as well as the plant height values which corresponded to each treatment were measured, for each weed species separately. These values were recorded at 1, 3 and 7 DAT, and expressed as percentages of the corresponding values recorded for the untreated control plants. 

An analysis of variance (ANOVA) combined over years and runs was conducted for all data and differences between means were compared at the 5% level of significance using the Fisher’s Protected LSD test. The ANOVA indicated no significant treatment x year interactions, across the two experimental runs, for each one of the weed species studied. Thus, the means of plant dry weight and height, for each weed species, were averaged over the two years and the two experimental runs. 
Afterwards, the pooled data were analyzed by ANOVA at a ≤5% probability level using Statgraphics® Centurion XVI. 

Fisher’s Protected LSD test was used to separate means regarding the effects of the application of the experimental treatments on plant dry weight and height for each one of the weed species studied. 

3. Results 3.1. Effects of the Experimental Treatments on L. rigidum Dry Weight and Height In the first measurement carried out at 1 DAT, it was noticed that PA3 reduced dry weight of rigid ryegrass by 41% as compared to the control whereas biomass reduction was by 13% higher in the case of PA1. 
The efficacy of manuka, lemongrass and pine essential oils was similar. 
The mixture of manuka oil and pelargonic acid resulted in 63% lower rigid ryegrass dry weight than the value recorded for the untreated plants whereas similar was the efficacy of the mixture of lemongrass essential oil and pelargonic acid. In the second measurement, carried out at 3 DAT, it was revealed that PA3 resulted in Agronomy 2020, 10, 1687 6 of 13 48% lower fresh weight compared to the untreated control. 
Rigid ryegrass dry weight was recorded at 34% and 37% of control when PA4 and EO3 treatments were applied, respectively. 
Manuka oil provided the highest efficacy of all the experimental treatments against rigid ryegrass. 

In the final measurement, carried out at 7 DAT, a 47% biomass reduction was recorded for PA3 as compared to the control. 

Increased was the efficacy of PA2 and pine oil application since rigid ryegrass dry weight was recorded at 30% and 33% of control. 

The mixture of lemongrass oil and pelargonic acid resulted in 77% lower dry weight in comparison to the value recorded for the control. 
Biomass reduction reached the level of 90% as compared to the control in the case of manuka oil and similar was the efficacy of manuka oil and pelargonic acid mixture (Table 3). 

Table 3. Dry weight and height of L. rigidum plants as affected by the application of the natural herbicides at 1, 3 and 7 days after treatment (DAT). 
Dry weight and height values of L. rigidum plants was expressed as % of control. 

Dry Weight (%) of Control Height (%) of Control Treatment 1 DAT 3 DAT 7 DAT 1 DAT 3 DAT 7 DAT PA1 46 b 42 ab 41 b 44 cb 43 b 40 ab PA2 34 d 29 cde 30 cd 38 bcd 27 def 28 cd PA3 59 a 52 a 53 a 63 a 54 a 51 a PA4 41 bcd 37 bcd 37 b 42 bcd 33 cde 35 bc EO1 41 bcd 27 de 10 e 45 b 28 cdef 8 e EO2 42 bc 39 bc 40 b 40 bcd 36 bc 38 bc EO3 38 cd 34 bcd 33 cd 37 de 35 bcd 36 bc M1 37 cd 22 e 6 e 36 e 24 f 7 e M2 36 cd 29 cde 23 d 40 bcd 26 ef 21 d LSD (0.05) 8 10 11 7 8 11 p value ** ** *** *** *** ** Different letters in the same column for L. rigidum dry weight and height, separately, indicate the significant differences between the means for each treatment at a = 5% significance level. **, *** = significant at 0.05, 0.01 and 0.001, respectively. 
At 1 DAT, height of rigid ryegrass was recorded at 63% of the untreated control when PA3 was applied. 
Lemongrass essential oil (EO2), PA2 and PA4 treatments resulted in 58–62% lower height as compared to the control. 
The efficacy of the manuka oil and pelargonic acid mixture as well as the efficacy of pine oil was similar and slightly increased in comparison to the three treatments mentioned above. 
In the second measurement carried out at 3 DAT, rigid ryegrass height was recorded at 43% of control in the case of PA1 whereas the adoption of PA2, PA4 and EO1 resulted in 67–73% in comparison to the control. 
Similar was the efficacy of the two mixtures used since height reduction reached the level of 74–76% as compared to the value recorded for the untreated plants and these two treatments were the most efficient against rigid ryegrass. In the final measurement carried out at 7 DAT, the efficacy of PA3 was similar to the two previous measurements whereas the application of lemongrass and pine oil resulted in 62–64% lower plant height as compared to the control. In addition, PA2 was even more effective since plant height was recorded at 28% of control in the case of this treatment. 

Manuka oil, as well as its mixture with pelargonic acid, were by far the most effective treatments since rigid ryegrass plant height was reduced by 92–93% (Table 3). 

3.2. Effects of the Experimental Treatments on A. sterilis Dry Weight and Height Regarding sterile oat, at 1 DAT it was observed that PA3 reduced dry weight by 52% as compared to the control. The efficacy of PA2 treatment was significantly higher than PA3. Essential oils derived from manuka, lemongrass and pine showed similar efficacy. 
The mixture of manuka oil and pelargonic acid (M1) was by approximately 6% more effective than the mixture of lemongrass oil and pelargonic acid (M2).
 At 3 DAT, it was noticed that sterile oat dry weight was recorded at 44% of control when PA3 treatment was applied while the corresponding value recorded under pine oil application was Agronomy 2020, 10, 1687 7 of 13 recorded at 35% of control. 
PA1 and PA4 treatments were more effective than PA3 treatment whereas lemongrass and manuka oils were characterized by similar efficacy. 
The most effective treatment was the mixture of manuka oil and pelargonic acid given that its application reduced dry weight by 82% as compared to the control. The results of the measurement carried out at 7 DAT clarified that PA3 was the least efficient treatment against sterile oat since weed biomass was recorded at 41% of control whereas the corresponding values recorded for PA4, PA1, EO2 and EO3 treatments ranged between 31 and 33% of control. The efficacy of the lemongrass oil and pelargonic acid mixture was significantly higher. 
Manuka oil resulted in a biomass reduction higher than 90% whereas the manuka oil and pelargonic acid mixture reduced weed biomass by 96% as compared to the value recorded for the untreated plants (Table 4). Table 4. Dry weight and height of A. sterilis plants as affected by the application of the natural herbicides at 1, 3 and 7 days after treatment (DAT). Dry weight and height values of A. sterilis plants was expressed as % of control. Dry Weight (%) of Control Height (%) of Control Treatment 1 DAT 3 DAT 1 DAT 3 DAT 1 DAT 3 DAT PA1 36 bcd 33 bc 33 ab 38 bc 36 b 35 ab PA2 27 e 24 de 23 bc 29 c 27 cde 24 cd PA3 48 a 44 a 41 a 53 a 46 a 42 a PA4 33 cde 30 bcd 31 ab 36 bc 33 bc 32 bc EO1 42 ab 28 bcd 7 de 44 ab 31 bcd 12 ef EO2 36 bcd 31 bcd 32 ab 37 bc 34 bc 34 ab EO3 39 bc 35 b 32 ab 42 b 37 b 35 ab M1 28 de 18 e 4 e 30 c 20 e 8 f M2 34 bcde 25 cde 17 cd 36 bc 25 de 19 de LSD (0.05) 9 8 11 9 7 9 p value * ** *** * ** *** Different letters in the same column for A. sterilis dry weight and height, separately, indicate the significant differences between the means for each treatment at a = 5% significance level. *, **, *** = significant at 0.05, 0.01 and 0.001, respectively. 
Sterile oat height was recorded at 53% of control when PA3 was applied as it was observed at 1 DAT. 
Sterile oat height ranged between 36% and 38% of control for PA4 and PA1 while almost the same plant height reduction was attributed to lemongrass essential oil application. 
Height reduction was estimated at 30% as compared to the value recorded for the untreated plants in the case of manuka oil and pelargonic acid mixture. 
This mixture was also approximately 6% more effective than the lemongrass oil and pelargonic acid mixture. 
At 3 DAT, PA3 remained the least effective of all the studied treatments given that its efficacy was lower than the corresponding of EO3, PA1 and PA4 treatments. 
The plant height values observed when manuka and lemongrass essential oils were applied were similar. 
PA2 application resulted in 73% lower sterile oat height as compared to the control. 
The efficacy of lemongrass oil and pelargonic acid mixture was similar, whereas mixing manuka oil and pelargonic acid was the most effective treatment of all against sterile oat. 
The final measurement carried out at 7 DAT confirmed that PA3 was the least effective treatment of all, while lemongrass and pine essential oils were more efficient than PA3 treatment. Mixing lemongrass oil with pelargonic acid was more effective than the treatments mentioned above. 

Manuka oil application was even more effective whereas its mixture with pelargonic acid resulted in the greatest plant height reduction which was recorded at 92% as compared to the control (Table 4). 3.3. Effects of the Experimental Treatments on G. aparine Dry Weight and Height In general, all the experimental treatments were more effective against cleaver than against the grass weeds studied. In particular, manuka and lemongrass essential oils provided a 67–70% biomass reduction in comparison to the control whereas biomass reduction for the two mixtures ranged between Agronomy 2020, 10, 1687 8 of 13 76% and 78% in comparison to the control as observed in the measurement carried out 24 h after treatment. The efficacy of all the pelargonic acid formulations was remarkable. At 3 DAT, it was observed that pine oil was 7% and 11% more effective than manuka and lemongrass essential oils, respectively, and the efficacy of the two mixtures was similar. PA3 treatment reduced weed biomass by 90%, whereas the application of PA2 treatment almost eliminated cleaver plants. 
At 7 DAT, the efficacy of lemongrass and pine oils was similar, whereas manuka oil was characterized by increased efficacy (up to 92%). 
PA4 and PA1 treatments resulted in a 96–97% dry weight reduction than the corresponding value recorded for the untreated plants. Weed dry weight was recorded at 6% of control in the case of lemongrass oil and pelargonic acid mixture whereas PA2 and M1 treatments completely eliminated cleaver plants (Table 5). 
Table 5. Dry weight and height of G. aparine plants as affected by the application of the natural herbicides at 1, 3 and 7 days after treatment (DAT). 
Dry weight and height values of G. aparine plants is expressed as % of control. 
Dry Weight (%) of Control Height (%) of Control Treatment 1 DAT 3 DAT 1 DAT 3 DAT 1 DAT 3 DAT PA1 12 def 5 cd 4 d 14 def 6 cd 6 cd PA2 5 f 2 d 0 d 8 f 4 d 0 d PA3 17 cde 10 bc 8 bc 20 cde 12 bc 11 bc PA4 10 ef 5 cd 3 d 13 ef 6 cd 5 cd EO1 33 a 23 a 8 bc 36 a 27 a 11 bc EO2 30 ab 27 a 25 a 33 ab 29 a 27 a EO3 19 cd 16 b 14 b 21 cd 19 b 18 b M1 22 c 12 b 0 d 25 c 13 bc 0 d M2 24 bc 15 b 6 bc 26 bc 16 b 8 cd LSD (0.05) 8 6 9 8 7 9 p value *** *** ** *** *** ** Different letters in the same column for G. aparine dry weight and height, separately, indicate the significant differences between the means for each treatment at a = 5% significance level. **, *** = significant at 0.05, 0.01 and 0.001, respectively. Cleaver height was by 64 and 67% lower compared to the control when manuka and lemongrass oils were applied, respectively, as noticed at 1 DAT. The efficacy of manuka oil and pelargonic acid were by 11% higher than the corresponding value of manuka oil alone and even higher was the efficacy of PA4 and PA1. PA2 treatment was the most effective of all the treatments studied, since its application reduced weed height by approximately 92% as compared to the control. 
The results of the second measurement revealed that cleaver height was recorded at 27% and 29% of control when manuka and lemongrass essential oils were applied, respectively. 
The mixture of lemongrass oil and pelargonic acid was characterized by similar efficacy to pine oil whereas PA3 treatment reduced plant height by almost 88% as compared to the control. 
At 7 DAT, it was noticed that lemongrass oil application was the least effective treatment against cleaver whereas pine oil was by 9% more effective. Cleaver height was only recorded at 5%, 6% and 8% of control when PA4, PA1 and M2 treatments were applied, while either manuka oil and pelargonic acid mixture or PA2 treatment completely eliminated cleaver plants (Table 5). 4. Discussion The results of the current study revealed the different efficacy of the four pelargonic acid products against the different weed species. 
In most cases, broadleaf weeds like cleaver were more susceptible than grass species, while the formulations of increased pelargonic acid concentration (e.g., PA2) were significantly more effective. Our findings are in contrast with the corresponding of Muñoz et al. [8] who noticed that all the pelargonic acid-based herbicides managed to completely eliminate Avena fatua (L.) plants at 3 DAT whereas there were no significant differences regarding the efficacy of the different Agronomy 2020, 10, 1687 9 of 13 pelargonic acid formulations. The insufficient control of rigid ryegrass and sterile oat when the low-concentration formulation of pelargonic acid was applied is in agreement with the findings of a previous study in which the application of pelargonic acid at the concentration of 2% (v/v) provided only 20% total weed control [14]. However, the same authors noticed that the same treatment controlled broadleaf weeds such as velvetleaf (Abutilon theophrastii Medic.) by only 31%. In our study, cleaver was adequately controlled by the majority of the pelargonic acid-based treatments even 24 h after treatment. 
Moreover, it was noticed that at 7 DAT, all the treatments did reduce cleaver dry biomass and plant height sufficiently. 
The possible effects of climatic conditions on the efficacy and the overall results is something that should be further studied. 
In our case, although weather conditions before and at spraying seemed favorable for the pot experiments, pelargonic acid products did not show remarkable efficacy against the two grass weed species. This outcome might be attributed to the air temperature at spraying time. The hypothesis of Krauss et al. [37] regarding the impact of weather conditions on the efficacy of pelargonic acid products was similar. 
In any case, this is an objective that should be systematically evaluated in future studies. 
In addition, there is evidence that various weed species can develop new shoots and recover after pelargonic acid application. 
Hence, another objective for a future experiment would be to find out the level of weed regrowth that emerges over a longer term than 7 DAT for a wider range of weed species. 
In fact, the natural substances are not translocated systemically in the plants and they cannot provide long-term weed control for most species. 
However, it has already been reported that sufficient weed control might be achieved with repeated treatments. 
Moreover, it was obvious that the different weed species’ responses to the application of the natural herbicides showed variability. 
This emphasizes the importance of further multifactor experiments towards the comparison of the effects of such experimental treatments between numerous weed species. 
The efficacy of pelargonic acid-based herbicides under real field conditions is an unexplored area of great interest. 
There are not many studies evaluating the level of weed control in the field and defining the crops that can be favored by the adoption of such weed control practices. 
However, there were interesting results in a more recent study carried out in Greece by Kanatas et al. in which pelargonic acid along with maleic hydrazide was applied for non-selective weed control before sowing soybean crop in a stale seedbed. In particular, it was revealed that stale seedbed combined with pelargonic acid application reduced annual weeds’ density by 95% as compared to normal seedbed, indicating that such pelargonic acid-based herbicides can be equally effective to glyphosate against annual weeds in a stale seedbed where a crop is about to be established and reap the benefits of pre-sowing weed elimination [19]. 
On one hand, it seems that integrated weed management strategies, including cultural practices such as the stale seedbed preparation, could maximize the herbicidal potential of pelargonic acid under real field conditions. 
Consequently, the level of weed control as assured by pelargonic acid-based herbicides could be sufficient if a vigorous and competitive crop is about to be sown. 
It has been reported recently in Greece that the competitiveness of barley (Hordeum vulgare L.) against troublesome weeds such as rigid ryegrass of sterile oat can be promoted if such organic weed control practices are applied before crop sowing [40]. 
On the other hand, after the nonanoic acid application, there was no weed cover reduction at one and two days after treatment in both experimental sites as well as repetitions in the field experiments of Martelloni et al. , where a treatment similar to PA-4 treatment was applied for weed control. 

The explanation suggested for this outcome was that weeds were in unsuitable growth stage for the natural herbicide to have an effect. 
Previous research has reported that nonanoic acid needs to be applied to very young or small plants for acceptable weed control, and repeated applications are suggested . 
However, in the current experiment, it was observed that increasing pelargonic acid concentration in a natural herbicide product can result in more efficient control for grasses and barely elimination of broadleaves. 
This finding is in agreement with the ones reported by Rowley et al., who observed an intermediate reduction in weed ground coverage, density, and dry weed biomass due to the higher rate of nonanoic acid used (39 L a.i. ha−1 ). Other authors found an intermediate reduction in Japanese stiltgrass (Microstegium vimineum Trin.) 
Agronomy 2020, 10, 1687 10 of 13 ground coverage as compared to their control treatment due to the pelargonic acid application at a rate of 11.8 kg a.i. ha−1 and 5% (v/v) concentration [44]. Concerning the potential role of maleic hydrazide, this was not statistically significant in the present study, probably due to the measurements being only for 7 days and not on a long-term basis. 

However, the use of products containing pelargonic acid along with maleic hydrazide is a promising tactic. 
An explanation might be given by the fact that maleic hydrazide has systemic activity and can be translocated in the meristematic tissues, with mobility in both phloem and xylem. 
Although its mode of action is not totally clear, it can be used effectively for the control of troublesome parasitic weed species belonging to Orobanche spp.. 
This is quite important, given that a factor restricting the herbicidal potential of pelargonic acid is the absence of systemic activity, with maleic hydrazide reducing weed regrowth and ensuring a long-term control. 

The findings of the present study also revealed that manuka oil is a possible solution for dealing with the challenge of increasing the systemic activity of natural herbicides. 
Even without being mixed with pelargonic acid, manuka oil showed increased efficacy against all the weeds as compared to the other essential oils and pelargonic acid treatments. In the study of Dayan et al. [32], it was noticed that manuka oil and its main active ingredient, leptospermone, were stable in soil for up to 7 d and had half-lives of 18 and 15 days after treatment, respectively. Such findings indicate the systemic activity of manuka oil and also that it can be a useful tool addressing many the restricting factors related to the use of natural herbicides. Dayan et al. [32] also recorded 68%, 57%, 93%, 88%, 73% and 50% lower biomass for pigweed (Amaranthus retroflexus L.), velvetleaf, field bindweed (Convolvulus arvensis L.), hemp sesbania [Sesbania exaltata (Raf.) Rydb. ex A.W. Hill], large crabgrass (Digitaria sanguinalis L.) and barnyardgrass (Echinochloa crus-galli L. P. Beauv.) as compared to the control, respectively, when a mixture with lemongrass essential oil was mixed with manuka oil and applied to the targeted weed species mentioned above. Pine and lemongrass essential oils provided a biomass reduction for rigid ryegrass and sterile oat ranging between 60% and 70% whereas they were more effective against the broad leaf species G. aparine. 
In the study of Young [45], pine oil controlled hairy vetch (Vicia villosa Roth), broadleaf filaree (Erodium botrys (Cav.) Bertol.), and hare barley (Hordeum murinum L.) at least 83%, but yellow starthistle (Centaurea solstitialis L.), soft brome (Bromus hordeaceus L.), control never surpassed the level of 85%. 
In the greenhouse experiment of Poonpaiboonpipat et al. [46], it was noted that lemongrass essential oil at concentrations of 1.25%, 2.5%, 5% and 10% (v/v) was phytotoxic against barnyard grass, since leaf wilt symptoms were observed at just 6 h after treatment. 

The same authors also noticed that chlorophyll a, b and carotenoid content decreased under increased concentrations of the essential oil, indicating that lemongrass essential oil interferes with the weeds’ photosynthetic metabolism [46]. 
Although the herbicidal potential of such essential oils does exist, many studies have concluded that there are limitations since the essential oils act as contact herbicides with no systemic activity [9,30,32,45,46]. 
They generally disrupt the cuticular layer of the foliage, which results in the rapid desiccation or burn-down of young tissues. 
However, lateral meristems tend to recover, and additional applications of essential oils are necessary to control regrowth. 


Essential oils must be applied at high concentrations to convey 50 to 500 L of active ingredient per hectare [30]. 
The limitations of applying either lemongrass or pine essential oils for weed control are similar to those mainly observed in the case of pelargonic acid-based herbicides. 
Manuka oil differs from other essential oils in that it contains large amounts of several natural b-triketones, including leptospermone, which enable this oil to have systemic activity [47]. 
One of the most important findings of the present study was the satisfactory control of all the targeted weed species in the case where the mixture of manuka oil and pelargonic acid was applied. This synergy resulted in improvement of overall weed control, compared to the cases in which pelargonic acid formulations, lemongrass and pine essential oils were used alone. 
This is one of the key findings of this study, and provides vital information for improving weed control in terms of either organic or sustainable agriculture. 
The findings of Coleman and Penner [14] were similar, finding that the addition of diammonium succinate and succinic acid improved the efficacy of a pelargonic acid formulation up to 200%, whereas l-Lactic acid and glycolic Agronomy 2020, 10, 1687 11 of 13 acid enhanced the efficacy of pelargonic acid formulations on velvetleaf and common lambsquarters (Chenopodium album L.) up to 138% even under real field conditions. 

5. Conclusions To date, no studies have evaluated the herbicidal potential of several pelargonic acid products, essential oils and mixtures of natural herbicides against major weed species in Greece. 
The findings of the present study revealed that selecting natural products with high concentrations of pelargonic acids can increase the control levels of grass weeds. 
However, in the case of broadleaf weeds, it seems that the application of natural products might lead to sufficient weed control even when products of lower pelargonic acid concentration are applied. The results of the current study also validated that lemongrass and pine oil act as contact burn-down herbicides, whereas manuka oil showed a systemic activity. 
The synergy between manuka oil and pelargonic acid is reported for the first time and is one of the key findings of the present study. 

This unique essential oil might deal with the lack of systemic activity associated with pelargonic acid and further experiments are in progress by our team. 
Further research is needed to evaluate more natural substances and combinations in order to optimize the use of natural herbicides as well as natural herbicides’ mixtures in weed management strategies in both organic and sustainable agriculture systems and also under different soil and climatic conditions.

Pelargonic Acid is a naturally-occurring saturated fatty acid with nine carbon atoms. The ammonium salt form of pelargonic acid is used as an herbicide. 
Pelargonic Acid works by stripping the waxy cuticle of the plant, causing cell disruption, cell leakage, and death by desiccation.

Pelargonic acid is a C9 straight-chain saturated fatty acid which occurs naturally as esters of the oil of pelargonium. 
Pelargonic acid has antifungal properties, and is also used as a herbicide as well as in the preparation of plasticisers and lacquers. 
Pelargonic acid has a role as an antifeedant, a plant metabolite, a Daphnia magna metabolite and an algal metabolite. 
Pelargonic acid is a straight-chain saturated fatty acid and a medium-chain fatty acid. It is a conjugate acid of a nonanoate. Nonanoic acid derives from a hydride of a nonane.


γ-nonanolactone has functional parent nonanoic acid 
(8R)-8-hydroxynonanoic acid has functional parent nonanoic acid 
(R)-2-hydroxynonanoic acid  has functional parent nonanoic acid 
1-nonanoyl-2-pentadecanoyl-sn-glycero-3-phosphocholine  has functional parent nonanoic acid 
1-octadecanoyl-2-nonanoyl-sn-glycero-3-phosphocholine  has functional parent nonanoic acid 
2-hydroxynonanoic acid  has functional parent nonanoic acid 
2-oxononanoic acid  has functional parent nonanoic acid 
7,8-diaminononanoic acid  has functional parent nonanoic acid 
8-amino-7-oxononanoic acid has functional parent nonanoic acid 
9-(methylsulfinyl)nonamide has functional parent nonanoic acid 
9-(methylsulfinyl)nonanoic acid has functional parent nonanoic acid 
9-aminononanoic acid has functional parent nonanoic acid 
9-hydroxynonanoic acid has functional parent nonanoic acid 
9-oxononanoic acid has functional parent nonanoic acid 
N-nonanoylglycine has functional parent nonanoic acid 
ethyl nonanoate has functional parent nonanoic acid 
hexadecafluorononanoic acid has functional parent nonanoic acid 
methyl nonanoate has functional parent nonanoic acid 
nonanal has functional parent nonanoic acid 
nonanoyl-CoA has functional parent nonanoic acid 
perfluorononanoic acid has functional parent nonanoic acid 
trimethylsilyl nonanoate has functional parent nonanoic acid 
nonanoate is conjugate base of nonanoic acid 
nonanoyl group is substituent group from nonanoic acid 

acid nonanoic (ro)
Acid nonanoic, acid pelargonic (ro)
acide nonanoique (fr)
Acide nonanoïque, acide pélargonique (fr)
acido nonanoico (it)
Acido nonanoico, acido pelargonico (it)
Aċidu nonanoiku, Aċidu pelargoniku (mt)
kwas nonanowy (pl)
Kwas nonanowy, kwas pelargonowy (pl)
kwas pelargonowy (pl)
Kyselina nonanová, kyselina pelargonová (cs)
kyselina nonánová (sk)
Kyselina nonánová (kyselina pelargónová) (sk)
Nonaanhape (et)
Nonaanhape, pelargoonhape (et)
Nonaanihappo (fi)
Nonaanihappo (pelargonihappo) (fi)
nonaanzuur (nl)
Nonaanzuur, pelar-goonzuur (nl)
nonano rūgštis (lt)
Nonano rūgštis, pelargono rūgštis (lt)
Nonanoic acid, Pelargonic acid (no)
nonanojska kislina (sl)
Nonanojska kislina, pelargonska kislina (sl)
nonanonska kiselina (hr)
nonanová kyselina (cs)
Nonanska kiselina, pelargonična kiselina (hr)
nonansyra (sv)
Nonansyra, pelargonsyra (sv)
nonansyre (da)
nonansyre (no)
Nonansyre og pelargonsyre (da)
Nonansäure (de)
Nonansäure, Pelargonsäure (de)
nonánsav (hu)
Nonánsav, pelargonsav (hu)
Nonānskābe (lv)
nonānskābe (lv)
ácido nonanoico (es)
Ácido nonanoico, ácido pelargónico (es)
ácido nonanóico (pt)
Ácido nonanóico, Ácido pelargónico (pt)
Εννεανικό οξύ (πελαργονικό οξύ) (el)
εννεανοϊκό οξύ (el)
нонанова киселина (bg)
Нонанова киселина, пеларгонова киселина (bg)


CAS names: Nonanoic acid

IUPAC names
Acid C9, Pelargonic acid
NONANOIC ACID
Nonanoic Acid
Nonanoic acid
nonanoic acid
nonanová kyselina
Nonansäure
Pelargonic acid
Pelargonic and realted fatty acids

Trade names
Acido Pelargónico
Pelargonic acid
Prifrac 2913
Prifrac 2914
Prifrac 2915

Synonyms

1-nonanoic acid
1752351 [Beilstein]
267-013-3 [EINECS]
506-25-2 [RN]
Acid C9
Acide nonanoïque [French] [ACD/IUPAC Name]
n-nonanoic acid
n-Nonylic acid
Nonanoic acid [ACD/Index Name] [ACD/IUPAC Name]
Nonansäure [German] [ACD/IUPAC Name]
n-Pelargonic acid
Pelargonic Acid
RA6650000
Pergonic acid
130348-94-6 [RN]
134646-27-8 [RN]
1-OCTANECARBOXYLIC ACID
4-02-00-01018 (Beilstein Handbook Reference) [Beilstein]
Cirrasol 185A
EINECS 203-931-2
EINECS 273-086-2
Emery 1203
Emery'S L-114
http://www.hmdb.ca/metabolites/HMDB0000847
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:29019
Jsp000917
KNA
KZH
MLS001066339
NCGC00164328-01
n-Nonanoic-9,9,9-d3 acid
n-Nonoic acid
Nonansaeure
noncarboxylic acid
nonoic acid
nonylic acid
Pelargic acid
pelargon
Pelargon [Russian]
Pelargon [Russian]
Pelargonic Acid 1202
Pelargonsaeure
SMR000112203
VS-08541
WLN: QV8

Synonym    Source
1-Nonanoate    
1-Nonanoic acid    ChEBI
1-Octanecarboxylate    
1-Octanecarboxylic acid    
CH3-[CH2]7-COOH    
Cirrasol 185a    
Emery 1202    
Emery'S L-114    
Emfac 1202    
FA(9:0)

Product name
Nonanoic acid (Pelargonic acid), Fatty acid
Description
Fatty acid.
Alternative names
Pelargonic acid
Biological description
Potent antifungal agent (IC50 = 50 μM against Trichophyton mentagrophytes). Inhibits spore germination and mycelial growth of pathogenic fungus. Active in vivo.

Nonanoic acid is now used relatively extensively as an herbicide in the home garden. A recent evaluation of an acute eye irritation study indicated moderate eye irritation following exposure to a product formulation containing 1.8% nonanoic acid.


Applications
Nonanoic acid is used in the preparation of plasticizers and lacquers. It is commonly used in conjunction with glyphosate, for a quick burn-down effect in the control of weeds in turfgrass.


Investigation of antimicrobial activities of nonanoic acid derivatives
January 2006Fresenius Environmental Bulletin 15(2):141-143

Abstract and Figures
In a search for promising antimicrobial compounds, seven derivatives of methyl-branched n-nonanoic acid (MNA) at positions 2, 3, 4, 5, 6, 7, and 8 have been synthesized, and antimicrobial activity is described. Anti-microbial activities were determined by using disk diffusion tests and expressed as MIC values for the n-nonanoic acid using the microdilution broth method in vitro against Bacillus subtilis, Mycobacterium smegmatis, Sarcina lutea, Escherichia coli, Salmonella typhimurium and Streptomyces nojiriensis for bacteria, and Candida utilis for fungi, and compared with Penicillin G and Polymyxin B. All compounds exhibit varied antimicrobial activity against Gram-positive bacteria, but remarkable inhibitory effects were observed against C. utilis and S. lutea in two compounds (2-MNA and 5-MNA). Interestingly, only 4-MNA, 7-MNA and 8-MNA possess activity against Streptomyces.

Synonyms
Pelargonic acid; 1-Octanecarboxylic acid; Cirrasol 185A; Cirrasol 185a; Emfac 1202; Hexacid C-9; Nonoic acid; Nonylic acid; Pelargic acid; Pelargon [Russian]; n-Nonanoic acid; n-Nonoic acid; n-Nonylic acid; [ChemIDplus]


Sources/Uses
Naturally occurs as an ester in oil of pelargonium; [Merck Index] Found in several essential oils; Used in lacquers, pharmaceuticals, plastics, and in esters for turbojet lubricants; Also used as a flavor and fragrance, flotation agent, gasoline additive, herbicide, blossom thinner for apple and pear trees, sanitizer, and to peel fruits and vegetables; [HSDB] Used to make peroxides and greases, as a catalyst for alkyd resins, in insect attractants, and as a topical bactericide and fungicide medication; [CHEMINFO]

Comments
Category of C7-C9 aliphatic aldehydes and carboxylic acids: Members and supporting chemicals demonstrate low acute toxicity by oral, dermal, and inhalation exposures; toxicity in repeated-dose studies only at relatively high levels; no evidence of reproductive toxicity, developmental toxicity, or mutagenicity; [EPA ChAMP: Hazard Characterization] Highly irritating; [Merck Index] A strong skin irritant; [Hawley] A skin and eye irritant; [HSDB] May cause permanent eye damage, including blindness; [CHEMINFO] Safe when used as a flavoring agent in food; [JECFA] A corrosive substance that can cause injury to the skin, eyes, and respiratory tract; [MSDSonline]

Use of nonanoic acid as an antimicrobial agent, in particular an antifungal agent
Abstract
The invention relates to the use of nonanoic acid as an antimicrobial, in particular antifungal, agent or additive, in particular in or for foods, such as dairy products or fruit juices. 
A particular aspect of the invention comprises the use of nonanoic acid i a cheese coating. 
The invention also relates to a cheese coating in which nonanoic acid has been incorporated as antifungal agent; a cheese that has been provided with such a coating; and a nonanoic acid-containing composition for applying such a coating. 
The nonanoic acid is used in particular on or close to the surface of the food, or uniformly distributed through the food, in an amount of 10 - 10,000 ppm, in particular 100 - 1,000 ppm. The nonanoic acid can furthermore be used as an antimicrobial agent for treating substrates or surfaces, in particular substrates or surfaces that come into contact with foods; for protecting foods, cut flowers and bulbs during transport and/or during storage; in disinfectants and cleaning agents; to protect or treat wood; in cosmetics or skin care products; and in pharmaceutical compositions to prevent and treat fungal infections and yeast infections , such as Candida.

Use of nonanoic acid as an antimicrobial agent, in particular an antifungal agent
The present invention relates to the use of nonanoic acid as an antimicrobial agent, in particular an antifungal agent. 
More particularly, the invention relates to the use of nonanoic acid as an antimicrobial agent, in particular an antifungal agent, in foods and in particular in dairy products such as cheese and products based on fruit, such as fruit juices.
The invention furthermore relates to foods which contain nonanoic acid as an antimicrobial agent. 
Particular aspects of the invention lie in the use of nonanoic acid in (solutions or suspensions for) cheese coatings, in the nonanoic acid-containing cheese coatings thus obtained and in the cheeses coated with these nonanoic acid-containing coatings.
The use of the nonanoic acid in food products is known. 

For instance, it is used as a synthetic flavouring in, for example, non-alcoholic drinks, ice cream, confectionery, gelatine, milk puddings and bakery products.
US Patent 2 154 449 describes the antifungal properties of C3 - CI2 carboxylic acids and salts thereof, in particular the incorporation of calcium propionate in bread dough in order to prevent the formation of mould on bread.
European Patent Application EP 0 244 144 A 1 teaches the addition of glyceryl fatty acid esters in combination with one or more C6.C,8 carboxylic acids as preservatives to, inter alia, food compositions.
International application WO 96/29895 describes a method for improving the shelf/storage life of perishable products by treating surfaces, equipment and materials, which come into contact with the products during the processing thereof, with an antimicrobial aromatic compound. 
WO 96/29895 states that fatty acids, including nonanoic acid, can also be used in combination with the aromatic compound.
International application WO 92/19104 teaches the use of C7 - C20 carboxylic acids, including nonanoic acid, for controlling infections in plants caused by bacteria and moulds. 
European Patent Application EP 0 022 289 relates to the incorporation of C3 - C, , carboxylic acids in polymers for the production of medical instruments, such as catheters.
European Patent Application EP 0 465 423 describes antimicrobial pharmaceutical preparations containing C4 - C,4 carboxylic acids. 
US Patent 4 406 884 describes antimicrobial pharmaceutical preparations for topical use which contain C5 - C,2 carboxylic acids.
US Patent 3 931 413 teaches the treatment of plants with C6 - C,8 carboxylic acids to combat infections by moulds which overwinter in the buds of the plants. 

Nonanoic acid is also used in some meat products to adjust the acidity. 

For instance, US Patent 4 495 208 describes a dog or cat food with good storage/shelf life which has a high moisture content (Aw > 0.9 and a water content of 50 - 80 %) that contains 4 -15 % (m/m) fructose, 0.3 - 3.0 % (m/m) of an edible organic acid, sufficient inorganic acid to obtain a pH in the range of 3.5 - 5.8 and an antifungal agent. 
The organic acid is preferably chosen from heptanoic acid, octanoic acid, nonanoic acid or a combination thereof.
In the animal feed according to US Patent 4 495 208 the edible organic acid is always present alongside a sugar (fructose) and an antifungal agent (antimycotic) known per se, such as sorbic acid and/or the salts thereof. 
It is stated that the combination of these three constituents in the indicated amounts gives a synergistic bactericidal action.
US Patent 3 985 904 describes a food based on meat which has a high moisture content and is suitable for human consumption or as an animal feed. 
This food has a moisture content of at least approximately 50 % (m m) and a water activity A,,, of at least approximately 0.90 and contains more than 50 % (m/m) of a ground, boiled, protein-like chicken, fish or meat material. 1 - 35 % (m m) of a gelatine-like filler based on starch, between 1.7 and 3.8 % of an edible, non-toxic acid and an effective amount of an antifungal agent.
The edible organic acid is incorporated in this food in an amount which is sufficient to bring the pH of the food to a value in the range from 3.9 to 5.5. 
Although US-A 3 985 904 mentions various suitable edible acids in column 6, nonanoic acid is not explicitly mentioned here.
According to US-A 3 985 904, the antifungal agent is chosen from benzoates, propionates and sorbate salts.
EP-A 0 876 768 describes the use of fatty acid monoesters of polyglycerol to improve the storage/shelf life of foods. 

Here the fatty acid radicals can be chosen from caproic acid, caprylic acid, lauric acid or myristic acid.
The use of nonanoic acid in herbicidal compositions for agricultural use is described, inter alia, in US Patents 5 098 467, 5 035 741, 5 106 410 and 5 975 4110. US Patents 4 820 438, 5 330 769 and 5 391 379 describe the use of nonanoic acid in soap and cleaning agents.
None of the above literature citations describes or suggests unambiguously that nonanoic acid can be safely incorporated in foods and/or can be used on foods in order to inhibit the growth of bacteria, moulds and yeasts. In particular, none of these literature citations teaches the dosage at which nonanoic acid can safely be used for this purpose.
Currently, natamycin is used as antifungal agent in cheese making. 

This compound, which is also designated pimaricin or "antibiotic A5283" and is marketed under the trade names Delvocid® and Natamax® (inter alia), is a metabolic product of Streptomyces natalensis and S. chattanoogensis.
However, the use of natamycin has a number of disadvantages. For instance it is fairly expensive. 
Moreover, it has been found that the mould Penicillium discolor is able to grow on (the surfaces of) cheeses treated with natamycin. 
This is particularly disadvantageous in the cheese industry, since P. discolor is widespread in cheese warehouses.
It has now been found that nonanoic acid displays an antimicrobial action, in particular an antifungal action, especially when it is used in amounts which can suitably be incorporated in food products. More particularly, it has been found that nonanoic acid can advantageously be used as an antimicrobial agent, in particular antifungal (fungicidal) agent, in dairy products such as cheese and products based on fruit, such as fruit juices.
The antimicrobial action of nonanoic acid found according to the invention is partly surprising because it is known that some types of mould (such as Aspergillus niger, Synchephalastrum racemosus, Geotrichum candidum, Penicillium expansum, Rhizopus stolonifer and Mucor plombus) naturally produce nonanoic acid. 
In addition, it has been found according to the invention that nonanoic acid is also able to inhibit the development of yeasts, which can likewise arise in cheese warehouses.
In a first aspect the invention therefore relates to the use of nonanoic acid (n-octane- 1 -carboxylic acid, pelargonic acid, n-nonylic acid) as an antimicrobial agent, in particular antifungal agent (additive) in or for foods and/or other products which have to be protected against perishing caused by microorganisms. 
The invention also relates to the use of salts of nonanoic acid as an antimicrobial agent.
The invention further relates to foods which contain nonanoic acid as an antimicrobial agent, in particular antifungal agent. 
The food can be any substance that is suitable for consumption by humans or animals, in particular for human consumption, and can be either a ready-to-eat food product or a constituent that can be incorporated in or processed to give a food product. The food or food product is in particular a product or substance that is susceptible to perishing caused by microorganisms, including bacteria, yeasts and in particular moulds (that is to say when no antimicrobial agent is added), such as, for example, a substance or product which will keep for between a few days and a few weeks (for example from 3 days to 3 weeks) under the customary conditions for storage of the product, such as a temperature in the range from room temperature (20 - 25 °C) down to refrigerator temperature (approximately 4 °C). However, the invention is not restricted to these.
In this context the nonanoic acid is used to inhibit microbial growth, in particular the formation of mould, and thus to extend the storage/shelf life. 
For instance, microbial growth can be retarded by the use of nonanoic acid. 
The degree of retardation will be dependent on, inter alia, the food, the nonanoic acid concentration, the conditions under which the food is stored (temperature, atmospheric humidity), the types of microorganisms to which the food is exposed and the degree of loading. 
In the case of mould formation, the mould formation (i.e. the point in time at which the first growth of mould is discernible to the naked eye) will in general be delayed by at least one day, preferably at least 5 - 7 days, that is to say at the temperature at which foods are usually stored - usually room temperature (20 °C) or in the refrigerator (4 °C) - compared with the untreated food. For instance, in the case of cheese that was coated with a nonanoic acid-containing coating according to the invention the first discernible formation of mould was postponed from 60 to 67 days. In this context reference is made to Example 1 below, as well as the results given in Figure 1. 
For the purposes of the invention, "inhibiting mould formation" and/or "antifungal" is preferably also understood to mean that the development of yeasts is (also) inhibited.
Moreover, it has been established according to the invention that nonanoic acid also has an antibacterial action, for example against bacteria which cause food to perish or otherwise reduce the quality thereof, and or against pathogens such as Listeria, Legionella, Salmonella and E.coli O157, Staphylococcus.
This inhibitory action of nonanoic acid on (the growth of) bacteria can also advantageously be employed in (the preparation of) fermented dairy products such as yoghurt. 
This will be explained in more detail below. The food can be a solid, semi-solid or fluid food and can be a fermented or non- fermented food.
A few non-limiting examples of foods in which nonanoic acid can be used according to the invention as an antimicrobial agent, in particular antifungal agent, are: - ready-to-eat food products, including dough products such as pre-baked bread, noodles, pasta, soups and the like; fish and meat products such as sausage, and products based on vegetables or fruit, such as fruit juices and canned fruit or combinations of fruit (juices) with dairy products; flour; nuts and (dried) southern fruits; and also products such as pre-prepared meals, diet foods, complete foods and baby food; foods and constituents for further processing, such as mayonnaise, ketchup and similar sauces; jam, marmalade and similar fruit preparations; and the like. According to the invention nonanoic acid can also be used outside the food sector as an antimicrobial agent, in particular antifungal and/or antibacterial agent, and examples of this will be given below.
One example that is worthy of mention at this juncture is the use of nonanoic acid or a nonanoic acid-containing coating to improve the storage/shelf life of fruit such as oranges, lemons, grapefruit, apples, pears and also nuts and (dried) southern fruits, coffee, tea, tobacco and the like, in particular before or during transport and/or during long-term storage, for example in a warehouse or a fruit store (which may or may not be air- conditioned).
When used as an antifungal agent according to the invention, the nonanoic acid will be used in an amount effective for the inhibition of moulds, yeasts and bacteria, which as a rule will be between 1 and 10,000 mg nonanoic acid per kg food, in particular 10-1,000 mg nonanoic acid per kg food and more particularly 100-500 mg nonanoic acid per kg food. 
Thus, for example, nonanoic acid can be used in yoghurt in an amount of approximately 200 milligram (mg) nonanoic acid per kilogram (kg) yoghurt. 
The lower limit for the effective amount of nonanoic acid will preferably be chosen from the series 10, 25, 50 or 100 mg nonanoic acid per kg food, whilst the upper limit is preferably chosen from the series 10,000, 5,000, 2,500, or 1,000 mg nonanoic acid per kg food.
Preferably, these amounts are based on the water content of the food. Thus, in the case of a food having a water content of 80 %, 80 % of the abovementioned amounts of nonanoic acid can also be added per kg food. The precise amount of nonanoic acid will, however, be dependent on the intended food and the way in which the nonanoic acid is used in the food. 

Thus, the nonanoic acid can be uniformly distributed throughout the entire food but, for example - especially in the case of solid or semi-solid foods - can also be present essentially only on or near the surface of the food, for example in the form of a nonanoic acid-containing antimicrobial, in particular antifungal, coating or surface layer, or as a result of treatment of the surface of the food with nonanoic acid. In these latter cases the concentration of nonanoic acid, based on the complete food, can be low (that is to say lower than the amounts indicated above), provided that sufficient nonanoic acid is present at or close to the surface in order to achieve the desired antimicrobial, in particular antifungal, action.
In general the presence of nonanoic acid in amounts of 10 - 10,000 ppm, in particular 100 - 2,000 ppm - i.e. locally or uniformly throughout the entire food - will be adequate to obtain the desired antimicrobial, in particular antifungal, action. The same concentrations of nonanoic acid - i.e. locally or uniformly throughout the entire food - will as a rule be sufficient to inhibit and/or to prevent the growth of yeast and/or of bacteria.
In a preferred aspect the food product is a dairy product, which in general is defined as a food based on milk or constituents of milk, in particular based on cows milk or constituents thereof. The dairy product is in particular a fermented dairy product that can be solid, semi- solid or fluid. 
A few non-limiting examples are cheese, butter, cream, yoghurt or yoghurt products (for example yoghurt drinks, such as, for example, milk/fruit juice drinks), cottage cheese, kefir, milk puddings and the like. 
The invention can also be employed in food products in which such dairy products have been incorporated/processed, such as sauces, pastries, desserts, foods (including complete food and baby food), snacks (for example containing cheese), meat products (such as ham in which proteins have been incorporated), powdered milk and coffee whiteners, and the like.
Use in cheese, and in particular in cheeses which have a low salt content (that is to say less than 4 %, in particular less than 3 %) and a high moisture content (that is to say 30 % or more, in particular 40 % or more) is to be particularly preferred. This can be carried out in particular by treating the surface of the cheese with nonanoic acid. 
Thus, the invention can (also) be used with feta, cheese spread and similar products.

The fermented dairy product preferably has a pH of 3.5 to 5.5, for example in the range of 5.1 - 5.5 for cheese and of 3.9 - 4.4 for yoghurt. 
Although it is not precluded that addition of nonanoic acid according to the invention makes some (usually minor) contribution to achieving this value, the final pH will as a rule be the result of the fermentation process and the buffer action possibly associated with this. 
In another preferred embodiment the food product is a fruit juice or similar drink, such as, for example, products in which dairy products such as milk or yoghurt and fruit juices have been processed, which have a limited shelf-life.
The nonanoic acid can be used in a manner known per se for antimicrobial agents, in particular antifungal agents, that is to say by adding the nonanoic acid or a nonanoic acid- containing additive to the food or food product, or incorporating the nonanoic acid or a nonanoic acid-containing additive in the food or food product, during and/or after the preparation thereof. During this operation the nonanoic acid can be uniformly mixed or distributed through the food and/or used on the surface of the food, for example by spraying or brushing with nonanoic acid (for example in the form of an aqueous solution), by immersing (in particular cheese) in a solution of nonanoic acid or by applying a nonanoic acid-containing coating. For this operation it is possible to use, for example, an aqueous solution or suspension of nonanoic acid or another nonanoic acid-containing, preferably liquid, mixture, which contains 100 - 5,000 ppm, in particular 200 to 3,000 ppm nonanoic acid and which furthermore can contain all constituents known per se for solutions for applying a cheese coating, such as (the constituents of) synthetic coatings known per se (for example based on copolymers) and/or coatings based on foodstuffs.
For instance - in a 140 gram coating for a 12.8 kg cheese - the nonanoic acid concentration in the coating can be 5,000 ppm (which corresponds to 49.2 mg nonanoic acid per kg cheese), 1,000 ppm (which corresponds to 9.8 mg/kg cheese) or 100 ppm (which corresponds to 0.98 mg/kg cheese).
The nonanoic acid-containing cheese coating thus obtained, the cheeses which have been provided with such nonanoic acid-containing cheese coatings and the nonanoic acid- containing solutions which are used in this operation form further aspects of the invention. 
In this context a further advantage of nonanoic acid is that it is also able to counteract and/or prevent too extensive development of the surface flora on the cheese (coating) - which can lead to the cheese rind being adversely affected - (this is in contrast to natamycin, that essentially is not able to exert any influence on bacterial growth).

As a rule the nonanoic acid will be used to replace the one or more antimicrobial, in particular antifungal, additives already used in a food known per se. 
In addition, the nonanoic acid can advantageously be used in those foods for which the known antimicrobial agents are unsuitable or less suitable. 
For such applications the use of nonanoic acid can form an alternative to the sterilisation treatments and/or similar antimicrobial treatment (that is to say other than the use of an antimicrobial additive) which are otherwise required.
Usually a single treatment of the food with nonanoic acid - such as the application of a nonanoic acid-containing coating - will be sufficient to obtain the desired antimicrobial action. However, repeated treatment of the food with nonanoic acid is not precluded. 
According to the invention nonanoic acid is used in particular to replace natamycin, in particular in applications in the dairy and cheese industries. In this regard reference is made, for example, to the applications of natamycin which are described by J. Stark in E>e Ware(n) Chemicus, 27 (1997), 173-176.
According to the invention nonanoic acid is highly preferentially compatible with the food, that is to say the use of nonanoic acid according to the invention has no adverse effect on the flavour, odour, consistency, pH or other desired characteristics of the food, at least not during the time that the food has to be or can be kept or stored prior to end use or consumption. 
As a rule this means that the food must be acid-resistant to a certain extent, that is to say at least must be able to withstand the pH that is obtained by the use of the nonanoic acid in the abovementioned amounts. In the event of possible problems with the compatibility, the use of a separate nonanoic acid-containing coating can offer a solution.
The food can furthermore contain all other additives known per se for the food, provided that these are compatible with nonanoic acid and do not adversely affect the antimicrobial action thereof. When nonanoic acid is used as antimicrobial agent according to the invention, as a rule no further antimicrobial agent will be required and according to one embodiment of the invention the food essentially contains exclusively nonanoic acid as antimicrobial agent, that is to say in the amounts specified above (in per cent by mass or ppm). 
However, it can not be entirely precluded that in addition to the nonanoic acid minor amounts of one or more further antimicrobial agents known per se are present, such as the agents which are mentioned below. Therefore, "essentially exclusively" is defined as meaning that the nonanoic acid makes up at least 80 % (m m), preferably at least 90 % (m/m) and more preferentially at least 95 - 99 % (m/m) of all antimicrobial constituents present (that is to say added to the food in order to achieve an antimicrobial action). 

Furthermore it is possible to use nonanoic acid in a mixture with one or more antimicrobial agents which are known per se and are compatible with nonanoic acid, a synergistic effect possibly being able to be obtained. In this case - compared with the use of the known agent as such - the nonanoic acid will as a rule replace some of the quantity of the known antimicrobial agent usually used. 

Nonanoic acid will as a rule make up at least 30 % (m/m), preferably at least 50 % (m/m) and more preferentially at least 70 % (m m) of the total antimicrobial constituents in such mixtures.
A few non-limiting examples of antimicrobial agents that can be used according to the invention in combination with nonanoic acid are: sorbic acid and salts thereof, benzoic acid and salts thereof, para-hydroxybenzoic acid or esters thereof, propionic acid and salts thereof, pimaricin, polyethylene glycol, ethylene/propylene oxides, sodium diacetate, caprylic acid (octanoic acid), ethyl formate, tylosin, polyphosphate, metabisulphite, nisin, subtilin and diethyl pyrocarbonate. 

The nonanoic acid can furthermore be used in combination with agents for adjusting the acidity, including the acids acceptable for foods, such as citric acid, acetic acid and the like. In this context the nonanoic acid can, in particular, protect the food (which in this case can have a pH in the range from 2 to 6) against acid-resistant moulds. Examples of such acid-resistant moulds are, but are not restricted to, Penicillium roqueforti, P. carneum, P. italicum, Monascus ruber and/or Paecilomyces variotii (which occur, for example, in rye bread); and Penicillium glandicola, Penicillium roqueforti, Aspergillus flavus, Aspergillus candidus and or Aspergillus terreus (which, for example, occur in products which have been preserved by acid, such as sour and/or sweet-sour preserves). More generally, according to the invention it is preferable that at least some, and preferably an appreciable proportion, of the nonanoic acid is present in the undissociated form in the food. 
The general rule in this context is that the amount of undissociated nonanoic acid increases at lower pH: for instance, approximately 90 % of the nonanoic acid is present in undissociated form at a pH of approximately 3.8.
According to one aspect of the invention, nonanoic acid is therefore also used in foods which have a low pH, such as a pH in the range 2 to 6, preferably 3 to 5.8, or 4 to 5.6. 
For instance, for example, the pH of cheese rind is around 4.8 - 5.3.
In addition to the antimicrobial, in particular antifungal, action described above, the use of nonanoic acid according to the invention can also yield the following further advantages: nonanoic acid is a stable molecule in both the dissociated and undissociated form.
The long alkyl chain is inert and renders the molecule barely reactive. nonanoic acid is a natural substance which occurs in plants, inter alia; - nonanoic acid has been approved for use in foods (inter alia by the FDA); nonanoic acid remains stable under the majority of processing steps/processes for food products; nonanoic acid is less susceptible to UV light than is, for example, natamycin; nonanoic acid is stable in the presence of metals in metallic form; - nonanoic acid is stable under heating.
The invention has been described above with reference to a preferred embodiment thereof; that is to say use in foods, in particular in dairy products. 
However, it will be clear to those skilled in the art from the above description that nonanoic acid can also find use outside the food sector as an antifungal, yeast-inhibiting and/or antibacterial agent. In this context it will, in particular, be an advantage that nonanoic acid has been approved for use in foods, so that it can be used in applications where it can come into contact with foods or the human body, such as with the skin.
A number of possible, non-limiting applications are: use as or in disinfectant(s), cleaning agent(s) and the like, for both domestic and industrial applications; disinfection and/or cleaning (including preventive treatment) of conveyor belts, pallets and the like; disinfection and/or cleaning (including preventive treatment) of apparatus, products and/or surfaces which come into contact with foods, such as cutting machines, mixers, stirrers, sorting equipment, filling machines and other equipment from the food processing industry; vats, dishes, tanks, plates, containers and other holders; and also worktops, sink units and the like; both domestic and industrial; disinfection and/or cleaning (including preventive treatment) of areas which may or may not be enclosed, in particular areas in which food products are processed and/or stored, such as cupboards, refrigerators, kitchens, factory areas, freight areas, warehouses and the like (both domestic and industrial); and in particular cheese warehouses and other commercial premises where P. discolor can occur; coating and/or (preventive) treatment of packaging for, for example, foods (such as fruit, vegetables, cheese and the like), for example made of materials such as plastic, paper, cardboard or shaped cardboard; protection of fruit, such as oranges, lemons, grapefruit, apples, pears; nuts and
(dried) southern fruits, coffee, tea, tobacco and the like, and also of cut flowers and bulbs, against moulds and/or bacteria, before or during transport and/or during (long- term) storage, for example in a warehouse or in an (optionally) air-conditioned fruit store; disinfection and/or cleaning (including preventive treatment) of, for example, tents or tarpaulins, and also indoors (for example on walls) to prevent or to counteract mould growth, for example as a consequence of damp; protection and/or treatment of wood and similar materials; use in cosmetics and skincare products; use for pharmaceutical applications, for example to prevent and treat fungal infections and yeast infections, such as Candida. These aspects of the invention in general comprise the treatment of a surface or substrate that is susceptible to mould formation, or that can be contaminated or infected by a mould and/or the spores thereof, with an amount of nonanoic acid which has an effective antifungal and/or antibacterial action.
This amount will differ depending on the application and the way in which the nonanoic acid is used on the surface or substrate. 
As a rule the presence of nonanoic acid in amounts of 10 - 10,000 ppm, in particular 100 - 2,000 ppm, will again be sufficient to achieve an antimicrobial, in particular antifungal, action, although higher concentrations can be used for some applications. The nonanoic acid can be used on the surface or substrate in any suitable way, such as, once again, spraying or brushing with nonanoic acid (for example in the form of an aqueous solution), by applying a nonanoic acid-containing coating or by use of an atomised spray containing nonanoic acid. 
This treatment can optionally be repeated.
In this context the nonanoic acid can once again be used instead of, or together with, disinfectants which may be known for the envisaged application, as well as in combination with other agents or constituents customary for the envisaged application. For these applications, the nonanoic acid and any other constituents can optionally be marketed in a suitable container, for example in a bottle or in the form of a spray.
A particular application of nonanoic acid according to the invention furthermore relates to the control - in particular the inhibition - of bacterial growth during fermentation processes, such as the preparation of fermented food products such as yoghurt. For this application use is made in particular of the antibacterial action of nonanoic acid. For instance, nonanoic acid can be used to control the pH during or after such fermentation processes and in particular to prevent and/or reduce post-acidification of, for example, yoghurt, as explained in more detail in the examples. 
The taste of the yoghurt is retained for longer as a result. 
In addition, the antimicrobial, in particular antifungal, action according to the invention will also be obtained.
The invention will now be explained with reference to the following non-limiting examples and the figures, in which:
Figure 1 is a graph (time against visible intensity of mould formation) in which the effect of nonanoic acid on mould formation on Gouda cheese is shown; Figure 2 is a graph (time against number of bacteria) which shows the effect of nonanoic acid (pelargonic acid) on the development of yoghurt bacteria at 7 °C; - 
Figure 3 is a graph (time against pH) which shows the effect of nonanoic acid (pelargonic acid) on the post-acidification of yoghurt at 7 °C; Figure 4 is a graph (time against number of bacteria) which shows the effect of nonanoic acid (pelargonic acid) on the development of yoghurt bacteria at 32 °C; Figure 5 is a graph (time against pH) which shows the effect of nonanoic acid (pelargonic acid) on the post-acidification of yoghurt at 32 °C;
Figure 6 is a plot (time against number of bacteria) that shows the influence of nonanoic acid (pelargonic acid) on the development of surface flora on cheese rind; Figure 7 is a plot (time against number) that shows the effect of nonanoic acid (pelargonic acid) on the development of D. hansenii, S. cereviseae, C. lipolytica and R. rubra;
Figures 8 A and 8B are photographs which show the effect of natamycin (Figure 8 A) and nonanoic acid (Figure 8B), respectively, on the inhibition of the growth of P. discolor on blocks of cheese rind;
Figure 9 is a graph (time against number of bacteria) which shows the effect of nonanoic acid on the growth of Bacillus cereus in soup;
Figure 10 is a graph (time against number of bacteria) which shows the effect of nonanoic acid on the growth of Staphylococcus aureus in soup;
Figure 11 is a graph (time against number of cells) which shows the effect of nonanoic acid on the growth of Debaromyces hansenii in a milk/fruit juice drink; Figure 2 is a graph (time against number of cells) which shows the effect of nonanoic acid on the growth of Penicillium italicum in a milk/fruit juice drink.

Experimental
Example 1 : Use of nonanoic acid in Gouda cheese
A trial production of Gouda cheeses was made. In this batch of cheeses one series was treated with 1000 ppm nonanoic acid (nonanoic acid) and the other series was not treated with a fungicide (blank). The two series were inoculated with spores of the mould P. discolor (0.1 spore/cm2) and stored at 13 °C and 88 % relative humidity. All individual cheeses were assessed visually at frequent intervals for the extent of the presence of mould. The following scale was used for the optical assessment of the intensity of visible moulds;
0 = no mould 1 = some mould
2 = distinct mould
3 = considerable mould
4 = very considerable mould or overgrown with mould.
The results are shown diagrammatically in Figure 1. In the case of the cheeses without fungicide slight mould growth (intensity 1) was detectable after about 60 days. 
In the case of the series of cheeses treated with nonanoic acid it was 66 days before mould growth (intensity 1) was observed.
Example 2: Use of nonanoic acid in yoghurt to prevent post-acidification In an experiment various concentrations of nonanoic acid were added to freshly prepared yoghurt. 
One series was monitored for 8 hours at the culture temperature (filling, 32 °C) and another series was incubated for 14 days at 7 °C (refrigerator temperature). 
This was carried out to investigate the extent to which nonanoic acid has an effect during yoghurt fermentation and/or during storage of the filled packs of yoghurt. 
For both series the pH was determined and the number of yoghurt bacteria.
The results are shown in Figures 2 - 5. Addition of 1,000 ppm nonanoic acid substantially prevented post-acidification (32 °C) and the number of yoghurt bacteria was reduced by 2 log units. At 7 °C an effect on the post-acidification was already detectable at lower nonanoic acid contents (200 ppm). Addition of 1,000 ppm prevented post- acidification Virtually completely when storing at refrigerator temperature and the number of yoghurt bacteria decreased by 4 log units.
Example 3: Effect of nonanoic acid on the surface flora of cheese rind
The effect of nonanoic acid on the surface flora on cheese rind was determined. 
The results (time against number of bacteria) are shown in Figure 6.
The effect of nonanoic acid (pelargonic acid) on the development of D. hansenii, S. cereviseae, C. lipolytica and R. rubra was also determined. 
The results (time against number) are shown in Figure 7.
Example 4: Use on blocks of cheese rind
In this experiment blocks of cheese rind were inoculated with P. discolor. The blocks were incubated at 20 °C and high relative humidity (95 %). These conditions were employed to provide the mould with the optimum opportunity to grow and are therefore more severe than the usual conditions for maturing cheese.
The results are given in Figure 8, which shows photographs of the blocks of cheese rind taken two weeks after inoculating with P. discolor. 
One series was treated with natamycin (Figure 8A) and the other series with nonanoic acid (Figure 8B). 
It can clearly be seen that after 2 weeks mould formation was inhibited in the blocks treated with nonanoic acid.
Example 5: Use in soup
In this experiment a creamy mushroom soup with parsley (chill-fresh product obtained from the Albert Heijn delicatessen in March 2000) was inoculated with
104 CFU/ml (colony-forming units per ml soup) of Bacillus cereus (NIZO B443) or with 104 CFU/ml Staphylococcus aureus (NIZO B1211). 
The soup was then incubated at 20 °C, without and with increasing concentrations of nonanoic acid (100, 500 and 1,000 ppm). 
Samples were taken at the times indicated in Figures 9 and 10 (Figure 9 for B. cereus and Figure 10 for S. aureus). 
From each sample a series of dilutions was plated to determine the number of CFU/ml soup. 

The B. cereus samples were plated on mannitol egg yolk polymyxin agar (MYP) and incubated for 24 hours at 30 °C; the S. aureus samples were plated on Baird-Parker egg yolk tellurite agar (BP) and incubated for 48 hours at 37 °C. The results are shown in Figures 9 and 10. The addition of 100 ppm nonanoic acid to the soup has a slightly inhibiting effect on the growth of both B. cereus and S. aureus, whilst with the addition of 500 or 1,000 ppm nonanoic acid the growth of both bacteria is virtually completely inhibited. Example 6: Use in a milk/fruit juice product
In this experiment a milk/fruit juice drink ("Milk & Fruit"™ from Coberco, obtained from Albert Heijn; "Milk & Fruit"™ is a chilled-fresh, pasteurised product without preservatives, consisting of 80 % drinking yoghurt and 20 % pineapple juice and has a pH value of 4.0) was inoculated with 102 CFU/ml Debaromyces hansenii (NIZO F937) or Penicillium italicum (CBS 278.58). 
The milk/fruit juice drink was then incubated at 20 °C, without and with increasing concentrations of nonanoic acid (100, 500 and 1,000 ppm). 
Samples were taken at the times indicated in Figures 11 and 12 (Figure 11 for D. hansenii and Figure 12 for P. italicum). 
For each sample a series of dilutions was plated in order to determine the number of CFU/ml drink. 
The samples were plated on oxytetracycline glucose yeast agar (OGY) and incubated for 5 days at 25 °C. 
The results are shown in Figures 11 and 12. Addition of 100 ppm nonanoic acid gives complete inhibition of the growth of D. hansenii. 
Addition of 100 or 500 ppm inhibits the growth of P. italicum and addition of 1,000 ppm nonanoic acid gives complete inhibition of the growth of P. italicum for up to 6 days.

GENERAL DESCRIPTION OF CARBOXYLIC ACID
Carboxylic acid is an organic compound whose molecules contain carboxyl group and have the condensed chemical formula R-C(=O)-OH in which a carbon atom is bonded to an oxygen atom by a solid bond and to a hydroxyl group by a single bond), where R is a hydrogen atom, an alkyl group, or an aryl group. Carboxylic acids can be synthesized if aldehyde is oxidized. Aldehyde can be obtained by oxidation of primary alcohol. Accordingly, carboxylic acid can be obtained by complete oxidation of primary alcohol. A variety of Carboxylic acids are abundant in nature and many carboxylic acids have their own trivial names. Examples are shown in table. In substitutive nomenclature, their names are formed by adding -oic acid' as the suffix to the name of the parent compound. The first character of carboxylic acid is acidity due to dissociation into H+ cations and RCOO- anions in aqueous solution. The two oxygen atoms are electronegatively charged and the hydrogen of a carboxyl group can be easily removed. The presence of electronegative groups next to the carboxylic group increases the acidity. For example, trichloroacetic acid is a stronger acid than acetic acid. Carboxylic acid is useful as a parent material to prepare many chemical derivatives due to the weak acidity of the hydroxyl hydrogen or due to the difference in electronegativity between carbon and oxygen. The easy dissociation of the hydroxyl oxygen-hydrogen provide reactions to form an ester with an alcohol and to form a water-soluble salt with an alkali. Almost infinite esters are formed through condensation reaction called esterification between carboxylic acid and alcohol, which produces water. The second reaction theory is the addition of electrons to the electron-deficient carbon atom of the carboxyl group. One more theory is decarboxylation (removal of carbon dioxide form carboxyl group). Carboxylic acids are used to synthesize acyl halides and acid anhydrides which are generally not target compounds. They are used as intermediates for the synthesis esters and amides, important derivatives from carboxylic acid in biochemistry as well as in industrial fields. There are almost infinite esters obtained from carboxylic acids. Esters are formed by removal of water from an acid and an alcohol. Carboxylic acid esters are used as in a variety of direct and indirect applications. Lower chain esters are used as flavouring base materials, plasticizers, solvent carriers and coupling agents. Higher chain compounds are used as components in metalworking fluids, surfactants, lubricants, detergents, oiling agents, emulsifiers, wetting agents textile treatments and emollients, They are also used as intermediates for the manufacture of a variety of target compounds. The almost infinite esters provide a wide range of viscosity, specific gravity, vapor pressure, boiling point, and other physical and chemical properties for the proper application selections. Amides are formed from the reaction of a carboxylic acids with an amine. Carboxylic acid's reaction to link amino acids is wide in nature to form proteins (amide), the principal constituents of the protoplasm of all cells. Polyamide is a polymer containing repeated amide groups such as various kinds of nylon and polyacrylamides. Carboxylic acid are in our lives.
ALIPHATIC CARBOXYLIC ACIDS

COMMON NAME

SYSTEMATIC NAME
CAS RN
FORMULA
MELTING POINT


Formic Acid    Methanoic acid    64-18-6    HCOOH
8.5 C


Acetic Acid    Ethanoic acid    64-19-7    CH3COOH    
16.5 C

Carboxyethane    Propionic Acid    79-09-4    CH3CH2COOH    
-21.5 C

Butyric Acid    n-Butanoic acid    107-92-6    CH3(CH2)2COOH    
-8 C

Valeric Acid    n-Pentanoic Acid    109-52-4    CH3(CH2)3COOH    
-19 C

Caproic Acid    n-Hexanoic Acid    142-62-1    CH3(CH2)4COOH    
-3 C

Enanthoic Acid    n-Heptanoic acid    111-14-8    CH3(CH2)5COOH    
-10.5 C

Caprylic Acid    n-Octanoic Acid    124-07-2    CH3(CH2)6COOH    
16 C

alpha-Ethylcaproic Acid    2-Ethylhexanoic Acid    149-57-5    CH3(CH2)3CH(C2H5)COOH    
-59 C

Valproic Acid    2-Propylpentanoic Acid    99-66-1    (CH3CH2CH2)2CHCOOH    
120 C

Pelargonic Acid    n-Nonanoic Acid    112-05-0    CH3(CH2)7COOH    
48 C

Capric Acid    n-Decanoic Acid    334-48-5    CH3(CH2)8COOH    
31 C


Nonanoic acid is a fatty acid which occurs naturally as esters are the oil of pelargonium. Synthetic esters, such as methyl nonanoate, are used as flavorings. Pelargonic acid is an organic compound composed of a nine-carbon chain terminating in a carboxylic acid. It is an oily liquid with an unpleasant, rancid odor. It is nearly insoluble in water, but well soluble in chloroform and ether.


Nonanoic acid, also called pelargonic acid, is an organic compound with structural formula CH3(CH2)7CO2H. It is a nine-carbon fatty acid. Nonanoic acid is a colorless oily liquid with an unpleasant, rancid odor. It is nearly insoluble in water, but very soluble in organic solvents. The esters and salts of nonanoic acid are called nonanoates. Its refractive index is 1.4322. Its critical point is at 712 K (439 °C) and 2.35 MPa.


PELARGONIC ACID = NONANOIC ACID = NONYLIC ACID = PELARGIC ACID


EC / List no.: 203-931-2
CAS no.: 112-05-0
Mol. formula: C9H18O2


Nonanoic acid (frequently referred to as pelargonic acid) is a naturally occurring carboxylic acid with a carbon chain-length of nine, belonging to the chemical class of saturated fatty acids commonly referred to as medium chain fatty acids (C8 to C12). 
Pelargonic acid is a clear, colourless liquid with a weak odour. 
Pelargonic acid (Nonanoic acid) is soluble in aqueous solutions however it can readily form esters and partially dissociate into the pelargonate anion (CH3(CH2)7COO-) and the hydronium cation (H3O+) in an aqueous solution. The molecular weight (158.24 g/mol) and octanol-water partition coefficient (3.4 logPow) of nonanoic acid suggest that dermal penetration is possible.


Nonanoic acid is a medium-chain saturated fatty acid. 
Nonanoic acid inhibits mycelial growth and spore germination in the plant pathogenic fungi M. roreri and C. perniciosa in a concentration-dependent manner.It has herbicidal activity against a variety of species, including crabgrass.
Nonanoic acid has been used as an internal standard for the quantification of free fatty acids in olive mill waste waters.
Formulations containing nonanoic acid have been used in indoor and outdoor weed control and as cleansing and emulsifying agents in cosmetics.

Pelargonic acid, also called nonanoic acid, is an organic compound with structural formula CH3(CH2)7CO2H. 
Pelargonic acid is a nine-carbon fatty acid. Nonanoic acid is a colorless oily liquid with an unpleasant, rancid odor. 
Pelargonic acid is nearly insoluble in water, but very soluble in organic solvents. 
The esters and salts of pelargonic acid are called pelargonates or nonanoates.

Pelargonic acid is used in herbicide formulations and in the preparation of plasticizers, resins, lubricants, and lacquers

Pelargonic acid or Nonanoic Acid is a C9 straight-chain saturated fatty acid which occurs naturally as esters of the oil of pelargonium. 
Pelargonic acid has antifungal properties, and is also used as a herbicide as well as in the preparation of plasticisers and lacquers.

Nonanoic Acid is a naturally-occurring saturated fatty acid with nine carbon atoms. The ammonium salt form of nonanoic acid is used as an herbicide. 
Nonanoic Acid works by stripping the waxy cuticle of the plant, causing cell disruption, cell leakage, and death by desiccation.

Nonanoic acid is a C9 straight-chain saturated fatty acid which occurs naturally as esters of the oil of pelargonium. 
Nonanoic acid has antifungal properties, and is also used as a herbicide as well as in the preparation of plasticisers and lacquers. 
Nonanoic acid has a role as an antifeedant, a plant metabolite, a Daphnia magna metabolite and an algal metabolite. 
Nonanoic acid is a straight-chain saturated fatty acid and a medium-chain fatty acid. It is a conjugate acid of a nonanoate. Nonanoic acid derives from a hydride of a nonane.

Nonanoic acid (Pelargonic acid, Nonoic acid) is a naturally occurring fatty acid found in both vegetable and animal fats.
Nonanoic acid (NNA) is a medium chain fatty acid, and is a naturally occurring carboxylic acid with a carbon chain length of nine. 
Nonanoic acid is used in agricultural and veterinary (AgVet) chemical products as an herbicide, and may have other uses in therapeutic goods or fragrances.

Nonanoic acid has been used in a range of agricultural chemicals as an herbicide, both in combination with other actives (particularly glyphosate), but also as a stand-alone active constituent. 
Commercial products are available with high concentrations of Nonanoic acid. Nonanoic acid is available as products for use in the home garden, both in ready to use formulations and also as concentrated formulations which require dilution prior to use.

Pelargonic acid, also known as nonanoic acid or pelargon, belongs to the class of organic compounds known as medium-chain fatty acids. 
These are fatty acids with an aliphatic tail that contains between 4 and 12 carbon atoms. 
Pelargonic acid is an oily liquid with an unpleasant, rancid odor. 
It is a very hydrophobic molecule, practically insoluble in water but very soluble in organic solvents. 
The biosynthesis of fatty acid occurs through the acetate pathway and the process is catalyzed by the Fatty Acid Synthase (FAS) enzymes. 
Structurally, FAS varies significantly across different organisms but essentially, they all perform the same task using the same mechanisms. 
Nonanoic acid is also used in the preparation of plasticizers and lacquers. Synthetic esters of nonanoic acid, such as methyl nonanoate, are used as flavorings. 
The derivative 4-nonanoylmorpholine is an ingredient in some pepper sprays. The ammonium salt of nonanoic acid, ammonium nonanoate, is an herbicide. 
It is commonly used in conjunction with glyphosate, a non-selective herbicide, to control weeds in turfgrass. 

Pelargonic acid is a clear to yellowish oily liquid. It is insoluble in water but soluble in ether, alcohol and organic solvents. 
The molecules of most natural fatty acids have an even number of carbon chains due to the linkage together by ester units. 
Analogous compounds of odd numbers carbon chain fatty acids are supplemented synthetically. 
Pelargonic acid, C-9 odd numbers carbon chain fatty acid, is relatively high cost fatty acid. 
Pelargonic acid can be prepared by ozonolysis which uses ozone is to cleave the alkene bonds. 
Example of ozonolysis in commerce is the production of odd carbon number carboxylic acids such as azelaic acid and pelargonic acid and simple carboxylic acids such as formic acid and oxalic acid.
Pelargonic acid forms esters with alcohols to be used as plasticizers and lubricating oils. 
It is used in modifying alkyd resins to prevent discolor and to keep flexibility and resistance to aging since saturated pelargonic acid will not be oxidized. 
Metallic soaps (barium and cadmium) and other inorganic salts used as a stabilizer. 
It is also used as a chemical intermediate for synthetic flavors, cosmetics, pharmaceuticals and corrosion inhibitors. 
It is known that C8 - C12 straight and saturated chain fatty acids are capable of removing the waxy cuticle of the broadleaf or weed, resulting in causing the tissue death. T
hey are used as active ingredient of environment friendly and quick effect herbicides. Pelargonic acid is the strongest one.


Nonanoic acid may be used to treat seizures (PMID 23177536).


Other names: n-Nonanoic acid; n-Nonoic acid; n-Nonylic acid; Nonoic acid; Nonylic acid; Pelargic acid; Pelargonic acid; 1-Octanecarboxylic acid; Cirrasol 185a; Emfac 1202; Hexacid C-9; Pelargon; Emery 1203; 1-Nonanoic acid; NSC 62787; n-Pelargonic acid; Emery 1202 (Salt/Mix)


IUPAC Name: nonanoic acid

Synonyms:      
1-nonanoic acid    
1-octanecarboxylic acid    
CH3‒[CH2]7‒COOH    IUPAC
n-nonanoic acid    
n-nonanoic acid    
Nonanoate    
Nonanoic acid    
Nonansäure Deutsch    
nonoic acid    
nonylic acid    
pelargic acid    
pelargon    
Pelargonic acid    
Pelargonsäure Deutsch    
pergonic acid

nonanoic acid has parent hydride nonane 
nonanoic acid has role Daphnia magna metabolite 
nonanoic acid has role algal metabolite 
nonanoic acid has role antifeedant 
nonanoic acid has role plant metabolite
nonanoic acid is a medium-chain fatty acid 
nonanoic acid is a straight-chain saturated fatty acid 
nonanoic acid is conjugate acid of nonanoate 

SYNONYMS :

NONANOIC ACID
Pelargonic acid
112-05-0
n-Nonanoic acid
Nonoic acid
Nonylic acid
Pelargic acid
n-Nonylic acid
n-Nonoic acid
1-Octanecarboxylic acid
Pelargon
Cirrasol 185A
Hexacid C-9
Emfac 1202
1-nonanoic acid
Fatty acids, C6-12
Fatty acids, C8-10
Nonansaeure
Pelargonsaeure
pergonic acid
MFCD00004433
nonoate
NSC 62787
UNII-97SEH7577T
68937-75-7
CH3-[CH2]7-COOH
CHEBI:29019
97SEH7577T
pergonate
n-nonanoate
1-nonanoate
C9:0
octan-1 carboxylic acid
1-octanecarboxylate
n-Nonanoic acid, 97%
DSSTox_CID_1641
DSSTox_RID_76255
DSSTox_GSID_21641
Pelargon [Russian]
1-Octanecarboxyic acid
CAS-112-05-0
FEMA No. 2784
HSDB 5554
EINECS 203-931-2
EPA Pesticide Chemical Code 217500
BRN 1752351
n-Pelargonate
AI3-04164
n-Nonylate
Perlargonic acid
n-Nonoate
n-pelargonic acid
KNA
EINECS 273-086-2
Nonanoic Acid Anion
Acid C9
Caprylic-Capric Acid
Nonanoic acid, 96%
3sz1
Emery's L-114
Pelargonic Acid 1202
Emery 1202
Emery 1203
octane-1-carboxylic acid

Preparation, occurrence, and uses
Pelargonic acid occurs naturally as esters in the oil of pelargonium. 
Together with azelaic acid, it is produced industrially by ozonolysis of oleic acid.

H17C8CH=CHC7H14CO2H + 4O → HO2CC7H14CO2H + H17C8CO2H
Synthetic esters of pelargonic acid, such as methyl pelargonate, are used as flavorings. 
Pelargonic acid is also used in the preparation of plasticizers and lacquers. 
The derivative 4-nonanoylmorpholine is an ingredient in some pepper sprays. 
The ammonium salt of pelargonic acid, ammonium pelargonate, is an herbicide. 
It is commonly used in conjunction with glyphosate, a non-selective herbicide, for a quick burn-down effect in the control of weeds in turfgrass.

Pharmacological effects
Pelargonic acid may be more potent than valproic acid in treating seizures.
Moreover, in contrast to valproic acid, pelargonic acid exhibited no effect on HDAC inhibition, suggesting that it is unlikely to show HDAC inhibition-related teratogenicity.

IUPAC name: Nonanoic acid
Other names: Nonoic acid; Nonylic acid;
1-Octanecarboxylic acid;
C9:0 (Lipid numbers)

Identifiers
CAS Number: 112-05-0 
EC Number: 203-931-2

Properties
Chemical formula: C9H18O2
Molar mass: 158.241 g·mol−1
Appearance: Clear to yellowish oily liquid
Density: 0.900 g/cm3
Melting point: 12.5 °C (54.5 °F; 285.6 K)
Boiling point: 254 °C (489 °F; 527 K)
Critical point (T, P): 439 °C (712 K), 2.35 MPa
Solubility in water: 0.3 g/L
Acidity (pKa): 4.96
1.055 at 2.06 to 2.63 K (−271.09 to −270.52 °C; −455.96 to −454.94 °F)
1.53 at −191 °C (−311.8 °F; 82.1 K)
Refractive index (nD): 1.4322

Hazards
Main hazards: Corrosive (C)
R-phrases (outdated): R34
S-phrases (outdated): (S1/2) S26 S28 S36/37/39 S45


Flash point: 114 °C (237 °F; 387 K)
Autoignition temperature: 405 °C


Categories: Alkanoic acids
Herbicides
Pelargonic Acid
Pelargonic acid is found naturally in pelargoniums and is a highly effective fatty acid widely used in the treatment of unwanted plants.

How does Pelargonic Acid work?
Pelargonic acid destroys the cell walls of the leaves of the weed. 

This results in the cells losing their structure and drying out within a short space of time, under normal conditions this will be visible within 1 day after treatment.

Only the green parts of the plant are affected by this action, the woody bark of the plant is unaffected as the cells are too stable and the active ingredient has no way of penetrating the surface. 
Therefore the product can be used under hedges, trees and bushes without fear of destroying the whole area.


Uses
Pelargonic acid occurs naturally in many plants and animals. 
Pelargonic acid is used to control the growth of weeds and as a blossom thinner for apple and pear trees. 
Pelargonic acid is also used as a food additive; as an ingredient in solutions used to commercially peel fruits and vegetables.


Pelargonic acid is present in many plants. 
Pelargonic acid is used as an herbicide to prevent growth of weeds both indoors and outdoors, and as a blossom thinner for apple and pear trees. 
The U.S. Food and Drug Administration (FDA) has approved this substance for use in food. 
No risks to humans or the environment are expected when pesticide products containing pelargonic acid are used according to the label directions. 

I. Description of the Active Ingredient Pelargonic acid is a chemical substance that is found in almost all species of animals and plants. 
Because it contains nine carbon atoms, it is also called nonanoic acid. 
It is found at low levels in many of the common foods we eat. 
It is readily broken down in the environment. 


II. Use Sites, Target Pests, And Application Methods Pelargonic acid has two distinct uses related to plants: weed killer and blossom thinner. 
[Note: The substance can also be used as a sanitizer, a use not addressed in this Fact Sheet.] 

o Weed killer Growers spray pelargonic acid on food crops and other crops to protect them against weeds. 
For food crops, pelargonic acid is allowed to be applied from planting time until 24 hours before harvest. 
The pre-harvest restriction assures that little or no residue remains on the food. 
The chemical also controls weeds at sites such as schools, golf courses, walkways, greenhouses, and various indoor sites. 

o Blossom thinner Growers use pelargonic acid to thin blossoms, a procedure that increases the quality and yield of apples and other fruit trees. 
Thinning the blossoms allows the trees to produce fruit every year instead of every other year. 


III. Assessing Risks to Human Health Pelargonic acid occurs naturally in many plants, including food plants, so most people are regularly exposed to small amounts of this chemical. 
The use of pelargonic acid as an herbicide or blossom thinner on food crops is not expected to increase human exposure or risk. 
Furthermore, tests indicate that ingesting or inhaling pelargonic acid in small amounts has no known toxic effects. 
Pelargonic acid is a skin and eye irritant, and product labels describe precautions that users should follow to prevent the products from getting in their eyes or on their skin.

THE USE OF PELARGONIC ACID AS A WEED MANAGEMENT TOOL 
Steven Savage and Paul Zomer Mycogen Corporation, San Diego, California In 1995, the Mycogen Corporation introduced Scythe®, a burn-down herbicide containing 60% of the active ingredient, pelargonic acid. 
Pelargonic acid is a naturally occurring, saturated, nine-carbon fatty acid (C9:0).

 Pelargonic acid occurs widely in nature in products such as goat's milk, apples and grapes. 

Commercially it is produced by the ozonolysis of oleic acid (C18:1) from beef tallow. 
Pelargonic acid has very low mammalian toxicity (oral, inhalation), is not mutagenic, teratogenic or sensitizing. 

It can cause eye and skin irritation and thus the formulated product carries a WARNING signal word (Category II). 

It has a benign environmental profile. As a herbicide, pelargonic acid causes extremely rapid and non-selective burn-down of green tissues. 

The rate of kill is related to temperature, but under all but the coolest conditions the treated plants begin to exhibit damage within 15-60 minutes and begin to collapse within 1-3 hours of the application. 

Pelargonic acid is not systemic and is not translocated through woody tissues. 
It is also active against mosses and other cryptograms. Pelargonic acid has no soil activity. 
As with most burn-down herbicides, pelargonic acid does not prevent re-growth from protected buds or basal meristems. 
Many annual herbaceous weeds can be killed completely while larger weeds, grasses and woody plants may re-grow. 
There are many practical applications of the rapid burn-down activity of pelargonic acid. 

It can be used for spot weeding, edging, lining, turf renewal, chemical pruning and suckering. 
It is particularly useful as a directed spray for killing annual weeds in container-grown woody ornamentals, under greenhouse benches and in other places where systemic herbicides can cause unwanted damage. 

If the spray of pelargonic acid does come in contact with some desired plants, the damage is strictly limited to those leaves which are actually sprayed. 

Pelargonic acid should be applied in at least 75 gallons/acre of total spray volume as activity declines at lower gallonages. 
Evidence from P31 NMR studies suggests that the mode of action of pelargonic acid is not based on direct damage to cell membranes. 
Pelargonic acid moves through the cuticle and cell membranes and lowers the internal pH of the plant cells. 
Over the next several minutes the pools of cellular ATP and Glucose-6-phosphate decline. 

Only later is there evidence of membrane dysfunction which eventually leads to cell leakage, collapse and desiccation of the tissue. 
This chain of cellular events appears to allow pelargonic acid to synergize the activity of certain systemic herbicides such as glyphosate. 

In general, bum-down herbicides are antagonistic to the activity of systemic herbicides, but in a tank mix pelargonic acid has been shown to allow greater and more rapid uptake of glyphosate without interfering with translocation. 
This type of synergy is completely distinct from the enhancement seen with various surfactants used as adjuvants or formulation components for glyphosate. 

By using high volume applications of a tank mix it is possible to combine the rapid kill of pelargonic acid with the systemic action of glyphosate. 

At low application volumes (e.g. 20-30 GPA), pelargonic acid still enhances glyphosate uptake and improves its overall performance, but there is no immediate burn of the treated foliage. 

Scythe herbicide was registered for non-crop use in 1995 and a crop registration is expected in 1996. 
This commercial formulation of pelargonic acid has a wide range of weed control applications both as a contact, non-selective agent and as a tank mixing partner with systemic herbicides such as glyphosate.

The Herbicidal Potential of Different Pelargonic Acid Products and Essential Oils against Several Important Weed Species 
Ilias Travlos 1,* , Eleni Rapti 1 , Ioannis Gazoulis 1 , Panagiotis Kanatas 2 , Alexandros Tataridas 1 , Ioanna Kakabouki 1 and Panayiota Papastylianou 1 1 
Laboratory of Agronomy, Department of Crop Science, Agricultural University of Athens, 75 Iera Odos str., 118 55 Athens, Greece; 

Published: 30 October 2020             

Abstract: There is growing consideration among farmers and researchers regarding the development of natural herbicides providing sufficient levels of weed control. 
The aim of the present study was to compare the efficacy of four different pelargonic acid products, three essential oils and two natural products’ mixtures against L. rigidum Gaud., A. sterilis L. and G. aparine L. Regarding grass weeds, it was noticed at 7 days after treatment that PA3 treatment (pelargonic acid 3.102% w/v + maleic hydrazide 0.459% w/v) was the least efficient treatment against L. rigidum and A. sterilis. The mixture of lemongrass oil and pelargonic acid resulted in 77% lower dry weight for L. rigidum in comparison to the control. Biomass reduction reached the level of 90% as compared to the control in the case of manuka oil and the efficacy of manuka oil and pelargonic acid mixture was similar. 
For sterile oat, weed biomass was recorded between 31% and 33% of the control for lemongrass oil, pine oil, PA1 (pelargonic acid 18.67% + maleic hydrazide 3%) and PA4 (pelargonic acid 18.67%) treatments. In addition, the mixture of manuka oil and pelargonic acid reduced weed biomass by 96% as compared to the control. 
Regarding the broadleaf species G. aparine, PA4 and PA1 treatments provided a 96–97% dry weight reduction compared to the corresponding value recorded for the untreated plants. 

PA2 (pelargonic acid 50% w/v) treatment and the mixture of manuka oil and pelargonic acid completely eliminated cleaver plants. 
The observations made for weed dry weight on the species level were similar to those made regarding plant height values recorded for each species. 

Further research is needed to study more natural substances and optimize the use of natural herbicides as well as natural herbicides’ mixtures in weed management strategies under different soil and climatic conditions. Keywords: bioherbicide; pelargonic acid; manuka oil; lemongrass oil; pine oil; grass weeds; broadleaf weeds 1. 
Introduction Weeds are considered to be one of the major threats to agricultural production since they affect the crop production indirectly, by competing with the crop for natural resources, sheltering crop pests, reducing crop yields and quality, and subsequently increasing the cost of processing [1]. Chemical control remains the most common control practice for weed management. Unfortunately, this overreliance on herbicides has led to serious problems, such as the possible injury to non-target vegetation and crops, the existence of herbicide residues in the water and the soil and concerns for human health and safety [2–5]. 
Another major issue associated with the use of synthetic herbicide is Agronomy 2020, 10, 1687; doi:10.3390/agronomy10111687 www.mdpi.com/journal/agronomy Agronomy 2020, 10, 1687 2 of 13 the growing problem of herbicide resistance since many harmful weed species including Amaranthus, Conyza, Echinochloa, and Lolium spp. are notorious for their ability to rapidly evolve resistance to a wide range of herbicide sites of action. 
The development of natural herbicides based on either organic acids or essential oils could decrease these negative impacts. 
They are less persistent in comparison to synthetic herbicides, more environmentally friendly, and they also have different modes of action which can prevent the development of herbicide-resistant weed biotypes [7,8]. Organic acids, essential oils, crude botanical products and other natural substances derived from plant tissues can be used as bio-herbicides in terms of weed management in both organic and sustainable agriculture systems [9]. 
Such natural substances face several opponents among the European Commission members, since there are doubts regarding the registration processes of natural products due to the lack of relevant toxicological data for their use at commercial scale [10]. Although these concerns might exist, there is evidence that most essential oils and their main compounds are not necessarily genotoxic or harmful to human health [11]. Such natural herbicides are sometimes less hazardous for environmental and human health in comparison to the commercial synthetic herbicides. 
In the case of pelargonic acid, toxicity tests on non-target organisms, such as birds, fish, and honeybees, revealed little or no toxicity. 
The chemical decomposes rapidly in both land and water environments, so it does not accumulate. 
To minimize drift and potential harm to non-target plants, users are required to take precautions such as avoiding windy days and using large spray droplets. 
However, product labels describe precautions that users should follow to prevent the products from getting in their eyes or on their skin since the acid is a skin and eye irritant [13]. 
Pelargonic acid (PA) (CH3(CH2)7CO2H, n-nonanoic acid) is a saturated, nine-carbon fatty acid (C9:0) naturally occurring as esters in the essential oil of Pelargonium spp. And can be derived from the tissues of various plant species [14–16]. Pelargonic acid along with its salts and formulated with emulsifiers is used in terms of weed management as a nonselective herbicide suitable either for garden or professional uses worldwide [8,14]. 
They are applied as contact burndown herbicides, which attack cell membranes and then as a result, cell leakage is caused and followed by membrane acyl lipids breakdown . 

The phytotoxic effects due to the application of pelargonic acid are visible in a very short time after spraying and the symptoms involve phytotoxicity for the plants and their cells, which rapidly begin to oxidize, and necrotic lesions are observed on the aerial parts of plants [18]. 
The potential use of pelargonic acid as a bioherbicide poses an attractive non-chemical weed control option which can be effectively integrated with other eco-friendly weed management strategies in important crops such as soybean [19]. Several commercial pelargonic acid-based natural herbicides include also maleic hydrazide (1,2-dihydro-3,6-pyridazinedione) which is a systemic plant growth regulator that has also been used as a herbicide since its introduction [20]. 

Maleic hydrazide (1, 2-dihydropyridazine-3, 6-dione), a hormone-like substance synthesized and first introduced to USA in 1949, with crystal structure and structural similarity to the pyrimidine base uracil [20–22]. 
After application to foliage, maleic hydrazide is translocated in the meristematic tissues, with mobility in both phloem and xylem. 
Although its mode of action is not clear, it can be used effectively for sprout suppression on vegetable crops such as onions and carrots as well as for the control of troublesome parasitic weed species where synthetic herbicides are limited [24–26]. Essential oils derived from a variety of aromatic, biomass, invasive or food crop plants are also known to have potential as natural non-selective herbicides [9,27–29]. 

Similarly, with the case of pelargonic acid, the foliage of weeds burns down in a very short time after application, which is more effective against young plants than older ones [30]. 
Manuka oil is isolated from the leaves of Leptospermum scoparium J. R. Forst. and G. Forst. and is considered to be an acceptable product in terms of organic standards [9]. 
The active ingredient in this essential oil is leptospermone, a natural b-triketone, which targets the enzyme p-hydroxyphenylpyruvate dioxygenase (HPPD) such as the conventional synthetic herbicides mesotrione and sulcotrione [31–33]. Lemongrass essential oil, derived from either Cymbopogon citratus Stapf. or C. flexuosus D.C. containing up to 80% citral is also commercialized Agronomy 2020, 10, 1687 3 of 13 as an organic herbicide whose mode of action involves the disruption of polymerization of plant microtubules [34]. 

Lemongrass oil acts as a contact herbicide, and since the active ingredient does not translocate, only the portions of plants receiving the spray solution are affected. 

Pine essential oil is also commercialized as a 10% aqueous emulsion for weed control as a natural herbicide. 

It is derived from steam distillation of needles, twigs and cones of Pinus sylvestris L. and a wide range of other species belonging to Pinus spp. and includes terpene alcohols and saponified fatty acids. Monoterpenes such as a- and b-pinene can increase the concentration of malondialdehyde, proline and hydrogen peroxide, indicating lipid peroxidation and induction of oxidative stress in weeds [35,36]. 
The aim of the present study was to evaluate and compare the efficacy of four different pelargonic acid products, three essential oils and two mixtures (of a pelargonic acid product and two essential oils) against three target weed species, i.e., rigid ryegrass (Lolium rigidum Gaud.), sterile oat (Avena sterilis L.) and cleaver (Galium aparine L.). 

2. Materials and Methods 2.1. Plant Material Collection and Seed Pretreatment Seeds of rigid ryegrass (L. rigidum), sterile oat (A. sterilis) and cleaver (G. aparine) were collected from winter wheat fields of the origins of Fthiotida, Viotia and Larisa, respectively, during June 2019 (Table 1). 
In each field, panicles and seeds were collected from 20 plants and transferred to the Laboratory of Agronomy (Agricultural University of Athens). 
Table 1. Weed species studied, origins and geographical positions where seed collection was carried out. Common Name Scientific Name Origin Position Rigid ryegrass Lolium rigidum Gaud. Fthiotida 39◦08007” N, 22◦24056” E Sterile oat Avena sterilis L. Viotia 38◦24041” N, 23◦00040” E Cleaver Galium aparine L. Larisa 39◦25051” N, 22◦45047” E Two experiments were conducted and repeated twice to evaluate and compare the efficacy of the different pelargonic acid products, essential oils and mixtures of natural herbicides against the three target weed species. 
The collected seeds were air-dried, threshed, placed in paper bags, and stored at room temperature to be used in the subsequent experimental runs. 
Different were the seed pretreatment processes carried out to release dormancy in the seeds of the grasses and in the seeds of cleaver. 

To release dormancy in the seeds of rigid ryegrass and sterile oat, the seeds were individually nicked with 2 teeth tweezers and placed in Petri dishes on two sheets of Whatman No.1 paper filter disk (Whatman Ltd., Maidstone, England) saturated with 6 mL distilled water, in 10 November. The Petri dishes were kept at 2–4 ◦C (refrigerator) for a period of 7 days. After that, the non-dormant seeds were used for sowing during the first experimental run, carried out during 2019. About half of the total collected grass weed seeds had been stored at room temperature to be used in the second experimental run, carried out during 2020. For cleaver, the seeds were sown in rectangular pots (28 × 30 × 70 cm3 ) and buried into the soil at approximately 3–4 cm depth, in 17 June. The pots were kept outside under natural conditions for 3 months to break the dormancy in the cleaver seeds. 
The seeds were carefully removed from the pots in 19 September. 
Afterwards, they were air-dried, placed and stored in paper bags at room temperature until use either for the first or the second experimental run. 
Approximately fifteen seeds of rigid ryegrass and sterile oat, and twenty seeds of cleaver were sown in separate pots (12 × 13 × 15 cm3 ) in 18 November 2019, during the experiments of the first run. Rigid ryegrass and sterile oat seeds were sown at 1 cm depth. 
Cleaver seeds were also sown at 1 cm depth to achieve maximum seedling emergence. 
Pots had been filled with a mix of herbicide–free soil from the experimental field of the Agricultural University of Athens and peat at the ratio of 1:1 (v/v). 
The soil of the experimental field is clay loam (CL) with pH value of 7.29, whereas the contents of CaCO3 and organic matter were 15.99% and 2.37%, respectively. 
Moreover, the concentrations of NO3 − Agronomy 2020, 10, 1687 4 of 13 P (Olsen) and Na+ were 104.3, 9.95 and 110 ppm, respectively. 
When the weed seedlings of all the weed species reached the appropriate phenological stage for spraying, they were carefully thinned to twelve plants per pot. 
All pots were watered as needed and placed outdoors. The pots were randomized every 5 days in order to achieve uniform growth conditions for all the plants. 
Regarding the duration of the first experiment, it was conducted between 18 November and 28 December 2019. 

Regarding the second experimental run, the pot experiments were established in 14 January 2020 and were conducted until 25 February 2020. 

For the second experimental run, the same courses of action were carried out regarding seed pretreatment and experiment establishment as compared to the corresponding ones carried out for the run. Typical climatic conditions for Greece were observed during the experimental periods. 
Maximum month temperatures for November, December, January and February were 21.3, 15.6, 9.2 and 11.3 ◦C, respectively. 
Minimum month temperatures for the same months were 14.2, 9.2, 2.1 and 1.8 ◦C, respectively, whereas total heights of precipitation for these months were 120.4, 90.6, 16.4 and 12.0 mm, respectively. 2.2. Experimental Treatments Several pelargonic acid products along with essential oils with a potential herbicidal action have been used. In particular, PA1 (3Stunden Bio-Unkrautfrei, Bayer Garten, Germany) and PA2 (Beloukha Garden, Belchim Crop Protection NV/SA, Technologielaan 7, 1840 Londerzeel, Belgium) contained only pelargonic acid at concentrations shown in Table 2, while PA3 and PA4 (Finalsan Ultima, W. Neudorff GmbH KG, Emmerthal, Germany) contained pelargonic acid along with maleic hydrazide (Table 2). For PA1, PA2, PA3 and PA4 treatments, pelargonic acid was applied as a single treatment without being mixed. Regarding the treatments containing essential oil application, EO1 (Manuka oil, Leptospermum scoparium, Salvia, India), EO2 (Lemon grass oil, Cymbopogon citratus, Sheer Essence, India) and EO3 (Pine oil, Pinus sylvestris, Sheer Essence, India) were used at 5% concentration. 
All of the essential oils were diluted with water before treatment to achieve a 5% concentration. 
In fact, commercial essential oils must be applied at high concentrations, often 10% or more per volume [30]. 

In the present study, an intermediate concentration of 5% was selected to reduce the cost of essential oil application in order to evaluate whether sufficient weed control can be achieved with the application of such natural herbicides at lower concentrations, acceptable also by an economic aspect. All herbicide applications were carried out with a handy pressure sprayer equipped with a variable conical nozzle. 

Spraying was carried out at 0.3 MPa pressure and the spraying angle was 80◦ . 
The height between the conical nozzle and the soil level was 40 cm for all the experimental treatments. 
The spray head was set to move over the plants at 1.5 km h−1 and the apparatus was calibrated to deliver the equivalent of 200 L ha−1 . 
The treatments were applied in 20 December, 2019, for the two runs of the first year (in 16 February 2020, for the two runs of the second year) when plants had reached the phenological stage of 2–3 true leaves, corresponding to stage 12–13 of the BBCH scale for rigid ryegrass and sterile oat, and the phenological stage of 3–4 true leaves, corresponding to stage 13–14 of the BBCH scale for cleaver. The pots were placed outdoors, and the leaves of the weed plants were vertically oriented at the time of spraying. 

The experimental treatments were carried out at a sunny day and air temperature during spraying was 16.1 ◦C, for the first year (13.4 ◦C for the second year). 

Table 2. The experimental treatments (e.g., natural herbicides) applied in the current study. 
Treatment Active Ingredient Content in (g/L) or (mL/L) Dose Rate (L/ha) Active Ingredient per Unit Area in (g/ha) or (mL/ha) Abbreviation Control - - - - 
Pelargonic acid 18.67% 18.67 1 200 3734 3 PA1 Pelargonic acid 50% 50 1 200 10000 3 PA2 Pelargonic acid 3.102% + maleic hydrazide 0.459% 3.102 1 200 620.4 3 PA3 Pelargonic acid 18.67% + maleic hydrazide 3% 18.67 1 + 3 1 200 3734 3 + 600 3 PA4 Agronomy 2020, 10, 1687 5 of 13 

Table 2. Cont. Treatment Active Ingredient Content in (g/L) or (mL/L) Dose Rate (L/ha) Active Ingredient per Unit Area in (g/ha) or (mL/ha) Abbreviation Manuka oil 5% 5 2 200 1000 4 EO1 Lemongrass oil 5% 5 2 200 1000 4 EO2 Pine oil 5% 5 2 200 1000 4 EO3 Pelargonic acid 18.67% + maleic hydrazide 3% + Manuka oil 5% 18.67 1 + 3 1 + 5 2 200 3734 3 + 600 3 + 1000 4 M1 Pelargonic acid 18.67% + maleic hydrazide 3% + Lemongrass oil 5% 18.67 1 + 3 1 + 5 2 200 3734 3 + 600 3 + 1000 4 M2 1 Data refer to the active ingredient contents of the four different pelargonic acid formulations. The active ingredients are expressed in g/L. 2 
Data refer to the active ingredient contents of the three different essential oil formulations. 
The active ingredients are expressed in mL/L. 3 Data refer to the amount of the active ingredient of the four different pelargonic acid formulations per unit area. 
The amounts are expressed in g/ha. 4 Data refer to the amount of the active ingredient of the three different essential oil formulations. 
The amounts are expressed in mL/ha. 

2.3. Evaluation of the Efficacy of Each Natural Herbicide against Targeted Weeds To evaluate the efficacy of each natural herbicide against the targeted weed species, dry weight and plant height of four plants per pot were measured for each weed species at 1, 3 and 7 days after treatment (DAT). 
For measuring dry weight, the selected plants were dried at 60 ◦C for 48 h and then the measurements of dry weight were carried out. 
The scale to measure dry weight had an accuracy of three decimal places and plant height was measured to nearest cm. 
Each one of the experiments started with twelve plants in each pot and four plants were removed from each pot at 1, 3 and 7 DAT. 
The assessment period was not longer than 7 DAT because the current experiment was focused on evaluating the knockdown effect of the natural herbicides on each one of the studied weed species. No observations regarding necrosis levels or NDVI values were made since these will be the objects of future experimentation. 2.4. Statistical Analysis Both of the experiments were repeated twice per year. 
All the experiments were conducted in a completely randomized design with four replicates and nine experimental treatments (PA1, PA2, PA3, PA4, EO1, EO2, EO3, M1 and M2). 

Four replicate pots were used for the evaluation of the effects of the experimental treatments on each weed species. 
For all the experiments, the weed dry weight as well as the plant height values which corresponded to each treatment were measured, for each weed species separately. These values were recorded at 1, 3 and 7 DAT, and expressed as percentages of the corresponding values recorded for the untreated control plants. 

An analysis of variance (ANOVA) combined over years and runs was conducted for all data and differences between means were compared at the 5% level of significance using the Fisher’s Protected LSD test. The ANOVA indicated no significant treatment x year interactions, across the two experimental runs, for each one of the weed species studied. Thus, the means of plant dry weight and height, for each weed species, were averaged over the two years and the two experimental runs. 
Afterwards, the pooled data were analyzed by ANOVA at a ≤5% probability level using Statgraphics® Centurion XVI. 

Fisher’s Protected LSD test was used to separate means regarding the effects of the application of the experimental treatments on plant dry weight and height for each one of the weed species studied. 

3. Results 3.1. Effects of the Experimental Treatments on L. rigidum Dry Weight and Height In the first measurement carried out at 1 DAT, it was noticed that PA3 reduced dry weight of rigid ryegrass by 41% as compared to the control whereas biomass reduction was by 13% higher in the case of PA1. 
The efficacy of manuka, lemongrass and pine essential oils was similar. 
The mixture of manuka oil and pelargonic acid resulted in 63% lower rigid ryegrass dry weight than the value recorded for the untreated plants whereas similar was the efficacy of the mixture of lemongrass essential oil and pelargonic acid. In the second measurement, carried out at 3 DAT, it was revealed that PA3 resulted in Agronomy 2020, 10, 1687 6 of 13 48% lower fresh weight compared to the untreated control. 
Rigid ryegrass dry weight was recorded at 34% and 37% of control when PA4 and EO3 treatments were applied, respectively. 
Manuka oil provided the highest efficacy of all the experimental treatments against rigid ryegrass. 

In the final measurement, carried out at 7 DAT, a 47% biomass reduction was recorded for PA3 as compared to the control. 

Increased was the efficacy of PA2 and pine oil application since rigid ryegrass dry weight was recorded at 30% and 33% of control. 

The mixture of lemongrass oil and pelargonic acid resulted in 77% lower dry weight in comparison to the value recorded for the control. 
Biomass reduction reached the level of 90% as compared to the control in the case of manuka oil and similar was the efficacy of manuka oil and pelargonic acid mixture (Table 3). 

Table 3. Dry weight and height of L. rigidum plants as affected by the application of the natural herbicides at 1, 3 and 7 days after treatment (DAT). 
Dry weight and height values of L. rigidum plants was expressed as % of control. 

Dry Weight (%) of Control Height (%) of Control Treatment 1 DAT 3 DAT 7 DAT 1 DAT 3 DAT 7 DAT PA1 46 b 42 ab 41 b 44 cb 43 b 40 ab PA2 34 d 29 cde 30 cd 38 bcd 27 def 28 cd PA3 59 a 52 a 53 a 63 a 54 a 51 a PA4 41 bcd 37 bcd 37 b 42 bcd 33 cde 35 bc EO1 41 bcd 27 de 10 e 45 b 28 cdef 8 e EO2 42 bc 39 bc 40 b 40 bcd 36 bc 38 bc EO3 38 cd 34 bcd 33 cd 37 de 35 bcd 36 bc M1 37 cd 22 e 6 e 36 e 24 f 7 e M2 36 cd 29 cde 23 d 40 bcd 26 ef 21 d LSD (0.05) 8 10 11 7 8 11 p value ** ** *** *** *** ** Different letters in the same column for L. rigidum dry weight and height, separately, indicate the significant differences between the means for each treatment at a = 5% significance level. **, *** = significant at 0.05, 0.01 and 0.001, respectively. 
At 1 DAT, height of rigid ryegrass was recorded at 63% of the untreated control when PA3 was applied. 
Lemongrass essential oil (EO2), PA2 and PA4 treatments resulted in 58–62% lower height as compared to the control. 
The efficacy of the manuka oil and pelargonic acid mixture as well as the efficacy of pine oil was similar and slightly increased in comparison to the three treatments mentioned above. 
In the second measurement carried out at 3 DAT, rigid ryegrass height was recorded at 43% of control in the case of PA1 whereas the adoption of PA2, PA4 and EO1 resulted in 67–73% in comparison to the control. 
Similar was the efficacy of the two mixtures used since height reduction reached the level of 74–76% as compared to the value recorded for the untreated plants and these two treatments were the most efficient against rigid ryegrass. In the final measurement carried out at 7 DAT, the efficacy of PA3 was similar to the two previous measurements whereas the application of lemongrass and pine oil resulted in 62–64% lower plant height as compared to the control. In addition, PA2 was even more effective since plant height was recorded at 28% of control in the case of this treatment. 

Manuka oil, as well as its mixture with pelargonic acid, were by far the most effective treatments since rigid ryegrass plant height was reduced by 92–93% (Table 3). 

3.2. Effects of the Experimental Treatments on A. sterilis Dry Weight and Height Regarding sterile oat, at 1 DAT it was observed that PA3 reduced dry weight by 52% as compared to the control. The efficacy of PA2 treatment was significantly higher than PA3. Essential oils derived from manuka, lemongrass and pine showed similar efficacy. 
The mixture of manuka oil and pelargonic acid (M1) was by approximately 6% more effective than the mixture of lemongrass oil and pelargonic acid (M2).
 At 3 DAT, it was noticed that sterile oat dry weight was recorded at 44% of control when PA3 treatment was applied while the corresponding value recorded under pine oil application was Agronomy 2020, 10, 1687 7 of 13 recorded at 35% of control. 
PA1 and PA4 treatments were more effective than PA3 treatment whereas lemongrass and manuka oils were characterized by similar efficacy. 
The most effective treatment was the mixture of manuka oil and pelargonic acid given that its application reduced dry weight by 82% as compared to the control. The results of the measurement carried out at 7 DAT clarified that PA3 was the least efficient treatment against sterile oat since weed biomass was recorded at 41% of control whereas the corresponding values recorded for PA4, PA1, EO2 and EO3 treatments ranged between 31 and 33% of control. The efficacy of the lemongrass oil and pelargonic acid mixture was significantly higher. 
Manuka oil resulted in a biomass reduction higher than 90% whereas the manuka oil and pelargonic acid mixture reduced weed biomass by 96% as compared to the value recorded for the untreated plants (Table 4). Table 4. Dry weight and height of A. sterilis plants as affected by the application of the natural herbicides at 1, 3 and 7 days after treatment (DAT). Dry weight and height values of A. sterilis plants was expressed as % of control. Dry Weight (%) of Control Height (%) of Control Treatment 1 DAT 3 DAT 1 DAT 3 DAT 1 DAT 3 DAT PA1 36 bcd 33 bc 33 ab 38 bc 36 b 35 ab PA2 27 e 24 de 23 bc 29 c 27 cde 24 cd PA3 48 a 44 a 41 a 53 a 46 a 42 a PA4 33 cde 30 bcd 31 ab 36 bc 33 bc 32 bc EO1 42 ab 28 bcd 7 de 44 ab 31 bcd 12 ef EO2 36 bcd 31 bcd 32 ab 37 bc 34 bc 34 ab EO3 39 bc 35 b 32 ab 42 b 37 b 35 ab M1 28 de 18 e 4 e 30 c 20 e 8 f M2 34 bcde 25 cde 17 cd 36 bc 25 de 19 de LSD (0.05) 9 8 11 9 7 9 p value * ** *** * ** *** Different letters in the same column for A. sterilis dry weight and height, separately, indicate the significant differences between the means for each treatment at a = 5% significance level. *, **, *** = significant at 0.05, 0.01 and 0.001, respectively. 
Sterile oat height was recorded at 53% of control when PA3 was applied as it was observed at 1 DAT. 
Sterile oat height ranged between 36% and 38% of control for PA4 and PA1 while almost the same plant height reduction was attributed to lemongrass essential oil application. 
Height reduction was estimated at 30% as compared to the value recorded for the untreated plants in the case of manuka oil and pelargonic acid mixture. 
This mixture was also approximately 6% more effective than the lemongrass oil and pelargonic acid mixture. 
At 3 DAT, PA3 remained the least effective of all the studied treatments given that its efficacy was lower than the corresponding of EO3, PA1 and PA4 treatments. 
The plant height values observed when manuka and lemongrass essential oils were applied were similar. 
PA2 application resulted in 73% lower sterile oat height as compared to the control. 
The efficacy of lemongrass oil and pelargonic acid mixture was similar, whereas mixing manuka oil and pelargonic acid was the most effective treatment of all against sterile oat. 
The final measurement carried out at 7 DAT confirmed that PA3 was the least effective treatment of all, while lemongrass and pine essential oils were more efficient than PA3 treatment. Mixing lemongrass oil with pelargonic acid was more effective than the treatments mentioned above. 

Manuka oil application was even more effective whereas its mixture with pelargonic acid resulted in the greatest plant height reduction which was recorded at 92% as compared to the control (Table 4). 3.3. Effects of the Experimental Treatments on G. aparine Dry Weight and Height In general, all the experimental treatments were more effective against cleaver than against the grass weeds studied. In particular, manuka and lemongrass essential oils provided a 67–70% biomass reduction in comparison to the control whereas biomass reduction for the two mixtures ranged between Agronomy 2020, 10, 1687 8 of 13 76% and 78% in comparison to the control as observed in the measurement carried out 24 h after treatment. The efficacy of all the pelargonic acid formulations was remarkable. At 3 DAT, it was observed that pine oil was 7% and 11% more effective than manuka and lemongrass essential oils, respectively, and the efficacy of the two mixtures was similar. PA3 treatment reduced weed biomass by 90%, whereas the application of PA2 treatment almost eliminated cleaver plants. 
At 7 DAT, the efficacy of lemongrass and pine oils was similar, whereas manuka oil was characterized by increased efficacy (up to 92%). 
PA4 and PA1 treatments resulted in a 96–97% dry weight reduction than the corresponding value recorded for the untreated plants. Weed dry weight was recorded at 6% of control in the case of lemongrass oil and pelargonic acid mixture whereas PA2 and M1 treatments completely eliminated cleaver plants (Table 5). 
Table 5. Dry weight and height of G. aparine plants as affected by the application of the natural herbicides at 1, 3 and 7 days after treatment (DAT). 
Dry weight and height values of G. aparine plants is expressed as % of control. 
Dry Weight (%) of Control Height (%) of Control Treatment 1 DAT 3 DAT 1 DAT 3 DAT 1 DAT 3 DAT PA1 12 def 5 cd 4 d 14 def 6 cd 6 cd PA2 5 f 2 d 0 d 8 f 4 d 0 d PA3 17 cde 10 bc 8 bc 20 cde 12 bc 11 bc PA4 10 ef 5 cd 3 d 13 ef 6 cd 5 cd EO1 33 a 23 a 8 bc 36 a 27 a 11 bc EO2 30 ab 27 a 25 a 33 ab 29 a 27 a EO3 19 cd 16 b 14 b 21 cd 19 b 18 b M1 22 c 12 b 0 d 25 c 13 bc 0 d M2 24 bc 15 b 6 bc 26 bc 16 b 8 cd LSD (0.05) 8 6 9 8 7 9 p value *** *** ** *** *** ** Different letters in the same column for G. aparine dry weight and height, separately, indicate the significant differences between the means for each treatment at a = 5% significance level. **, *** = significant at 0.05, 0.01 and 0.001, respectively. Cleaver height was by 64 and 67% lower compared to the control when manuka and lemongrass oils were applied, respectively, as noticed at 1 DAT. The efficacy of manuka oil and pelargonic acid were by 11% higher than the corresponding value of manuka oil alone and even higher was the efficacy of PA4 and PA1. PA2 treatment was the most effective of all the treatments studied, since its application reduced weed height by approximately 92% as compared to the control. 
The results of the second measurement revealed that cleaver height was recorded at 27% and 29% of control when manuka and lemongrass essential oils were applied, respectively. 
The mixture of lemongrass oil and pelargonic acid was characterized by similar efficacy to pine oil whereas PA3 treatment reduced plant height by almost 88% as compared to the control. 
At 7 DAT, it was noticed that lemongrass oil application was the least effective treatment against cleaver whereas pine oil was by 9% more effective. Cleaver height was only recorded at 5%, 6% and 8% of control when PA4, PA1 and M2 treatments were applied, while either manuka oil and pelargonic acid mixture or PA2 treatment completely eliminated cleaver plants (Table 5). 4. Discussion The results of the current study revealed the different efficacy of the four pelargonic acid products against the different weed species. 
In most cases, broadleaf weeds like cleaver were more susceptible than grass species, while the formulations of increased pelargonic acid concentration (e.g., PA2) were significantly more effective. Our findings are in contrast with the corresponding of Muñoz et al. [8] who noticed that all the pelargonic acid-based herbicides managed to completely eliminate Avena fatua (L.) plants at 3 DAT whereas there were no significant differences regarding the efficacy of the different Agronomy 2020, 10, 1687 9 of 13 pelargonic acid formulations. The insufficient control of rigid ryegrass and sterile oat when the low-concentration formulation of pelargonic acid was applied is in agreement with the findings of a previous study in which the application of pelargonic acid at the concentration of 2% (v/v) provided only 20% total weed control [14]. However, the same authors noticed that the same treatment controlled broadleaf weeds such as velvetleaf (Abutilon theophrastii Medic.) by only 31%. In our study, cleaver was adequately controlled by the majority of the pelargonic acid-based treatments even 24 h after treatment. 
Moreover, it was noticed that at 7 DAT, all the treatments did reduce cleaver dry biomass and plant height sufficiently. 
The possible effects of climatic conditions on the efficacy and the overall results is something that should be further studied. 
In our case, although weather conditions before and at spraying seemed favorable for the pot experiments, pelargonic acid products did not show remarkable efficacy against the two grass weed species. This outcome might be attributed to the air temperature at spraying time. The hypothesis of Krauss et al. [37] regarding the impact of weather conditions on the efficacy of pelargonic acid products was similar. 
In any case, this is an objective that should be systematically evaluated in future studies. 
In addition, there is evidence that various weed species can develop new shoots and recover after pelargonic acid application. 
Hence, another objective for a future experiment would be to find out the level of weed regrowth that emerges over a longer term than 7 DAT for a wider range of weed species. 
In fact, the natural substances are not translocated systemically in the plants and they cannot provide long-term weed control for most species. 
However, it has already been reported that sufficient weed control might be achieved with repeated treatments. 
Moreover, it was obvious that the different weed species’ responses to the application of the natural herbicides showed variability. 
This emphasizes the importance of further multifactor experiments towards the comparison of the effects of such experimental treatments between numerous weed species. 
The efficacy of pelargonic acid-based herbicides under real field conditions is an unexplored area of great interest. 
There are not many studies evaluating the level of weed control in the field and defining the crops that can be favored by the adoption of such weed control practices. 
However, there were interesting results in a more recent study carried out in Greece by Kanatas et al. in which pelargonic acid along with maleic hydrazide was applied for non-selective weed control before sowing soybean crop in a stale seedbed. In particular, it was revealed that stale seedbed combined with pelargonic acid application reduced annual weeds’ density by 95% as compared to normal seedbed, indicating that such pelargonic acid-based herbicides can be equally effective to glyphosate against annual weeds in a stale seedbed where a crop is about to be established and reap the benefits of pre-sowing weed elimination [19]. 
On one hand, it seems that integrated weed management strategies, including cultural practices such as the stale seedbed preparation, could maximize the herbicidal potential of pelargonic acid under real field conditions. 
Consequently, the level of weed control as assured by pelargonic acid-based herbicides could be sufficient if a vigorous and competitive crop is about to be sown. 
It has been reported recently in Greece that the competitiveness of barley (Hordeum vulgare L.) against troublesome weeds such as rigid ryegrass of sterile oat can be promoted if such organic weed control practices are applied before crop sowing [40]. 
On the other hand, after the nonanoic acid application, there was no weed cover reduction at one and two days after treatment in both experimental sites as well as repetitions in the field experiments of Martelloni et al. , where a treatment similar to PA-4 treatment was applied for weed control. 

The explanation suggested for this outcome was that weeds were in unsuitable growth stage for the natural herbicide to have an effect. 
Previous research has reported that nonanoic acid needs to be applied to very young or small plants for acceptable weed control, and repeated applications are suggested . 
However, in the current experiment, it was observed that increasing pelargonic acid concentration in a natural herbicide product can result in more efficient control for grasses and barely elimination of broadleaves. 
This finding is in agreement with the ones reported by Rowley et al., who observed an intermediate reduction in weed ground coverage, density, and dry weed biomass due to the higher rate of nonanoic acid used (39 L a.i. ha−1 ). Other authors found an intermediate reduction in Japanese stiltgrass (Microstegium vimineum Trin.) 
Agronomy 2020, 10, 1687 10 of 13 ground coverage as compared to their control treatment due to the pelargonic acid application at a rate of 11.8 kg a.i. ha−1 and 5% (v/v) concentration [44]. Concerning the potential role of maleic hydrazide, this was not statistically significant in the present study, probably due to the measurements being only for 7 days and not on a long-term basis. 

However, the use of products containing pelargonic acid along with maleic hydrazide is a promising tactic. 
An explanation might be given by the fact that maleic hydrazide has systemic activity and can be translocated in the meristematic tissues, with mobility in both phloem and xylem. 
Although its mode of action is not totally clear, it can be used effectively for the control of troublesome parasitic weed species belonging to Orobanche spp.. 
This is quite important, given that a factor restricting the herbicidal potential of pelargonic acid is the absence of systemic activity, with maleic hydrazide reducing weed regrowth and ensuring a long-term control. 

The findings of the present study also revealed that manuka oil is a possible solution for dealing with the challenge of increasing the systemic activity of natural herbicides. 
Even without being mixed with pelargonic acid, manuka oil showed increased efficacy against all the weeds as compared to the other essential oils and pelargonic acid treatments. In the study of Dayan et al. [32], it was noticed that manuka oil and its main active ingredient, leptospermone, were stable in soil for up to 7 d and had half-lives of 18 and 15 days after treatment, respectively. Such findings indicate the systemic activity of manuka oil and also that it can be a useful tool addressing many the restricting factors related to the use of natural herbicides. Dayan et al. [32] also recorded 68%, 57%, 93%, 88%, 73% and 50% lower biomass for pigweed (Amaranthus retroflexus L.), velvetleaf, field bindweed (Convolvulus arvensis L.), hemp sesbania [Sesbania exaltata (Raf.) Rydb. ex A.W. Hill], large crabgrass (Digitaria sanguinalis L.) and barnyardgrass (Echinochloa crus-galli L. P. Beauv.) as compared to the control, respectively, when a mixture with lemongrass essential oil was mixed with manuka oil and applied to the targeted weed species mentioned above. Pine and lemongrass essential oils provided a biomass reduction for rigid ryegrass and sterile oat ranging between 60% and 70% whereas they were more effective against the broad leaf species G. aparine. 
In the study of Young [45], pine oil controlled hairy vetch (Vicia villosa Roth), broadleaf filaree (Erodium botrys (Cav.) Bertol.), and hare barley (Hordeum murinum L.) at least 83%, but yellow starthistle (Centaurea solstitialis L.), soft brome (Bromus hordeaceus L.), control never surpassed the level of 85%. 
In the greenhouse experiment of Poonpaiboonpipat et al. [46], it was noted that lemongrass essential oil at concentrations of 1.25%, 2.5%, 5% and 10% (v/v) was phytotoxic against barnyard grass, since leaf wilt symptoms were observed at just 6 h after treatment. 

The same authors also noticed that chlorophyll a, b and carotenoid content decreased under increased concentrations of the essential oil, indicating that lemongrass essential oil interferes with the weeds’ photosynthetic metabolism [46]. 
Although the herbicidal potential of such essential oils does exist, many studies have concluded that there are limitations since the essential oils act as contact herbicides with no systemic activity [9,30,32,45,46]. 
They generally disrupt the cuticular layer of the foliage, which results in the rapid desiccation or burn-down of young tissues. 
However, lateral meristems tend to recover, and additional applications of essential oils are necessary to control regrowth. 


Essential oils must be applied at high concentrations to convey 50 to 500 L of active ingredient per hectare [30]. 
The limitations of applying either lemongrass or pine essential oils for weed control are similar to those mainly observed in the case of pelargonic acid-based herbicides. 
Manuka oil differs from other essential oils in that it contains large amounts of several natural b-triketones, including leptospermone, which enable this oil to have systemic activity [47]. 
One of the most important findings of the present study was the satisfactory control of all the targeted weed species in the case where the mixture of manuka oil and pelargonic acid was applied. This synergy resulted in improvement of overall weed control, compared to the cases in which pelargonic acid formulations, lemongrass and pine essential oils were used alone. 
This is one of the key findings of this study, and provides vital information for improving weed control in terms of either organic or sustainable agriculture. 
The findings of Coleman and Penner [14] were similar, finding that the addition of diammonium succinate and succinic acid improved the efficacy of a pelargonic acid formulation up to 200%, whereas l-Lactic acid and glycolic Agronomy 2020, 10, 1687 11 of 13 acid enhanced the efficacy of pelargonic acid formulations on velvetleaf and common lambsquarters (Chenopodium album L.) up to 138% even under real field conditions. 

5. Conclusions To date, no studies have evaluated the herbicidal potential of several pelargonic acid products, essential oils and mixtures of natural herbicides against major weed species in Greece. 
The findings of the present study revealed that selecting natural products with high concentrations of pelargonic acids can increase the control levels of grass weeds. 
However, in the case of broadleaf weeds, it seems that the application of natural products might lead to sufficient weed control even when products of lower pelargonic acid concentration are applied. The results of the current study also validated that lemongrass and pine oil act as contact burn-down herbicides, whereas manuka oil showed a systemic activity. 
The synergy between manuka oil and pelargonic acid is reported for the first time and is one of the key findings of the present study. 

This unique essential oil might deal with the lack of systemic activity associated with pelargonic acid and further experiments are in progress by our team. 
Further research is needed to evaluate more natural substances and combinations in order to optimize the use of natural herbicides as well as natural herbicides’ mixtures in weed management strategies in both organic and sustainable agriculture systems and also under different soil and climatic conditions.

Pelargonic Acid is a naturally-occurring saturated fatty acid with nine carbon atoms. The ammonium salt form of pelargonic acid is used as an herbicide. 
Pelargonic Acid works by stripping the waxy cuticle of the plant, causing cell disruption, cell leakage, and death by desiccation.

Pelargonic acid is a C9 straight-chain saturated fatty acid which occurs naturally as esters of the oil of pelargonium. 
Pelargonic acid has antifungal properties, and is also used as a herbicide as well as in the preparation of plasticisers and lacquers. 
Pelargonic acid has a role as an antifeedant, a plant metabolite, a Daphnia magna metabolite and an algal metabolite. 
Pelargonic acid is a straight-chain saturated fatty acid and a medium-chain fatty acid. It is a conjugate acid of a nonanoate. Nonanoic acid derives from a hydride of a nonane.


γ-nonanolactone has functional parent nonanoic acid 
(8R)-8-hydroxynonanoic acid has functional parent nonanoic acid 
(R)-2-hydroxynonanoic acid  has functional parent nonanoic acid 
1-nonanoyl-2-pentadecanoyl-sn-glycero-3-phosphocholine  has functional parent nonanoic acid 
1-octadecanoyl-2-nonanoyl-sn-glycero-3-phosphocholine  has functional parent nonanoic acid 
2-hydroxynonanoic acid  has functional parent nonanoic acid 
2-oxononanoic acid  has functional parent nonanoic acid 
7,8-diaminononanoic acid  has functional parent nonanoic acid 
8-amino-7-oxononanoic acid has functional parent nonanoic acid 
9-(methylsulfinyl)nonamide has functional parent nonanoic acid 
9-(methylsulfinyl)nonanoic acid has functional parent nonanoic acid 
9-aminononanoic acid has functional parent nonanoic acid 
9-hydroxynonanoic acid has functional parent nonanoic acid 
9-oxononanoic acid has functional parent nonanoic acid 
N-nonanoylglycine has functional parent nonanoic acid 
ethyl nonanoate has functional parent nonanoic acid 
hexadecafluorononanoic acid has functional parent nonanoic acid 
methyl nonanoate has functional parent nonanoic acid 
nonanal has functional parent nonanoic acid 
nonanoyl-CoA has functional parent nonanoic acid 
perfluorononanoic acid has functional parent nonanoic acid 
trimethylsilyl nonanoate has functional parent nonanoic acid 
nonanoate is conjugate base of nonanoic acid 
nonanoyl group is substituent group from nonanoic acid 

acid nonanoic (ro)
Acid nonanoic, acid pelargonic (ro)
acide nonanoique (fr)
Acide nonanoïque, acide pélargonique (fr)
acido nonanoico (it)
Acido nonanoico, acido pelargonico (it)
Aċidu nonanoiku, Aċidu pelargoniku (mt)
kwas nonanowy (pl)
Kwas nonanowy, kwas pelargonowy (pl)
kwas pelargonowy (pl)
Kyselina nonanová, kyselina pelargonová (cs)
kyselina nonánová (sk)
Kyselina nonánová (kyselina pelargónová) (sk)
Nonaanhape (et)
Nonaanhape, pelargoonhape (et)
Nonaanihappo (fi)
Nonaanihappo (pelargonihappo) (fi)
nonaanzuur (nl)
Nonaanzuur, pelar-goonzuur (nl)
nonano rūgštis (lt)
Nonano rūgštis, pelargono rūgštis (lt)
Nonanoic acid, Pelargonic acid (no)
nonanojska kislina (sl)
Nonanojska kislina, pelargonska kislina (sl)
nonanonska kiselina (hr)
nonanová kyselina (cs)
Nonanska kiselina, pelargonična kiselina (hr)
nonansyra (sv)
Nonansyra, pelargonsyra (sv)
nonansyre (da)
nonansyre (no)
Nonansyre og pelargonsyre (da)
Nonansäure (de)
Nonansäure, Pelargonsäure (de)
nonánsav (hu)
Nonánsav, pelargonsav (hu)
Nonānskābe (lv)
nonānskābe (lv)
ácido nonanoico (es)
Ácido nonanoico, ácido pelargónico (es)
ácido nonanóico (pt)
Ácido nonanóico, Ácido pelargónico (pt)
Εννεανικό οξύ (πελαργονικό οξύ) (el)
εννεανοϊκό οξύ (el)
нонанова киселина (bg)
Нонанова киселина, пеларгонова киселина (bg)


CAS names: Nonanoic acid

IUPAC names
Acid C9, Pelargonic acid
NONANOIC ACID
Nonanoic Acid
Nonanoic acid
nonanoic acid
nonanová kyselina
Nonansäure
Pelargonic acid
Pelargonic and realted fatty acids

Trade names
Acido Pelargónico
Pelargonic acid
Prifrac 2913
Prifrac 2914
Prifrac 2915

Synonyms

1-nonanoic acid
1752351 [Beilstein]
267-013-3 [EINECS]
506-25-2 [RN]
Acid C9
Acide nonanoïque [French] [ACD/IUPAC Name]
n-nonanoic acid
n-Nonylic acid
Nonanoic acid [ACD/Index Name] [ACD/IUPAC Name]
Nonansäure [German] [ACD/IUPAC Name]
n-Pelargonic acid
Pelargonic Acid
RA6650000
Pergonic acid
130348-94-6 [RN]
134646-27-8 [RN]
1-OCTANECARBOXYLIC ACID
4-02-00-01018 (Beilstein Handbook Reference) [Beilstein]
Cirrasol 185A
EINECS 203-931-2
EINECS 273-086-2
Emery 1203
Emery'S L-114
http://www.hmdb.ca/metabolites/HMDB0000847
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:29019
Jsp000917
KNA
KZH
MLS001066339
NCGC00164328-01
n-Nonanoic-9,9,9-d3 acid
n-Nonoic acid
Nonansaeure
noncarboxylic acid
nonoic acid
nonylic acid
Pelargic acid
pelargon
Pelargon [Russian]
Pelargon [Russian]
Pelargonic Acid 1202
Pelargonsaeure
SMR000112203
VS-08541
WLN: QV8

Synonym    Source
1-Nonanoate    
1-Nonanoic acid    ChEBI
1-Octanecarboxylate    
1-Octanecarboxylic acid    
CH3-[CH2]7-COOH    
Cirrasol 185a    
Emery 1202    
Emery'S L-114    
Emfac 1202    
FA(9:0)

Product name
Nonanoic acid (Pelargonic acid), Fatty acid
Description
Fatty acid.
Alternative names
Pelargonic acid
Biological description
Potent antifungal agent (IC50 = 50 μM against Trichophyton mentagrophytes). Inhibits spore germination and mycelial growth of pathogenic fungus. Active in vivo.

Nonanoic acid is now used relatively extensively as an herbicide in the home garden. A recent evaluation of an acute eye irritation study indicated moderate eye irritation following exposure to a product formulation containing 1.8% nonanoic acid.


Applications
Nonanoic acid is used in the preparation of plasticizers and lacquers. It is commonly used in conjunction with glyphosate, for a quick burn-down effect in the control of weeds in turfgrass.


Investigation of antimicrobial activities of nonanoic acid derivatives
January 2006Fresenius Environmental Bulletin 15(2):141-143

Abstract and Figures
In a search for promising antimicrobial compounds, seven derivatives of methyl-branched n-nonanoic acid (MNA) at positions 2, 3, 4, 5, 6, 7, and 8 have been synthesized, and antimicrobial activity is described. Anti-microbial activities were determined by using disk diffusion tests and expressed as MIC values for the n-nonanoic acid using the microdilution broth method in vitro against Bacillus subtilis, Mycobacterium smegmatis, Sarcina lutea, Escherichia coli, Salmonella typhimurium and Streptomyces nojiriensis for bacteria, and Candida utilis for fungi, and compared with Penicillin G and Polymyxin B. All compounds exhibit varied antimicrobial activity against Gram-positive bacteria, but remarkable inhibitory effects were observed against C. utilis and S. lutea in two compounds (2-MNA and 5-MNA). Interestingly, only 4-MNA, 7-MNA and 8-MNA possess activity against Streptomyces.

Synonyms
Pelargonic acid; 1-Octanecarboxylic acid; Cirrasol 185A; Cirrasol 185a; Emfac 1202; Hexacid C-9; Nonoic acid; Nonylic acid; Pelargic acid; Pelargon [Russian]; n-Nonanoic acid; n-Nonoic acid; n-Nonylic acid; [ChemIDplus]


Sources/Uses
Naturally occurs as an ester in oil of pelargonium; [Merck Index] Found in several essential oils; Used in lacquers, pharmaceuticals, plastics, and in esters for turbojet lubricants; Also used as a flavor and fragrance, flotation agent, gasoline additive, herbicide, blossom thinner for apple and pear trees, sanitizer, and to peel fruits and vegetables; [HSDB] Used to make peroxides and greases, as a catalyst for alkyd resins, in insect attractants, and as a topical bactericide and fungicide medication; [CHEMINFO]

Comments
Category of C7-C9 aliphatic aldehydes and carboxylic acids: Members and supporting chemicals demonstrate low acute toxicity by oral, dermal, and inhalation exposures; toxicity in repeated-dose studies only at relatively high levels; no evidence of reproductive toxicity, developmental toxicity, or mutagenicity; [EPA ChAMP: Hazard Characterization] Highly irritating; [Merck Index] A strong skin irritant; [Hawley] A skin and eye irritant; [HSDB] May cause permanent eye damage, including blindness; [CHEMINFO] Safe when used as a flavoring agent in food; [JECFA] A corrosive substance that can cause injury to the skin, eyes, and respiratory tract; [MSDSonline]

Use of nonanoic acid as an antimicrobial agent, in particular an antifungal agent
Abstract
The invention relates to the use of nonanoic acid as an antimicrobial, in particular antifungal, agent or additive, in particular in or for foods, such as dairy products or fruit juices. 
A particular aspect of the invention comprises the use of nonanoic acid i a cheese coating. 
The invention also relates to a cheese coating in which nonanoic acid has been incorporated as antifungal agent; a cheese that has been provided with such a coating; and a nonanoic acid-containing composition for applying such a coating. 
The nonanoic acid is used in particular on or close to the surface of the food, or uniformly distributed through the food, in an amount of 10 - 10,000 ppm, in particular 100 - 1,000 ppm. The nonanoic acid can furthermore be used as an antimicrobial agent for treating substrates or surfaces, in particular substrates or surfaces that come into contact with foods; for protecting foods, cut flowers and bulbs during transport and/or during storage; in disinfectants and cleaning agents; to protect or treat wood; in cosmetics or skin care products; and in pharmaceutical compositions to prevent and treat fungal infections and yeast infections , such as Candida.

Use of nonanoic acid as an antimicrobial agent, in particular an antifungal agent
The present invention relates to the use of nonanoic acid as an antimicrobial agent, in particular an antifungal agent. 
More particularly, the invention relates to the use of nonanoic acid as an antimicrobial agent, in particular an antifungal agent, in foods and in particular in dairy products such as cheese and products based on fruit, such as fruit juices.
The invention furthermore relates to foods which contain nonanoic acid as an antimicrobial agent. 
Particular aspects of the invention lie in the use of nonanoic acid in (solutions or suspensions for) cheese coatings, in the nonanoic acid-containing cheese coatings thus obtained and in the cheeses coated with these nonanoic acid-containing coatings.
The use of the nonanoic acid in food products is known. 

For instance, it is used as a synthetic flavouring in, for example, non-alcoholic drinks, ice cream, confectionery, gelatine, milk puddings and bakery products.
US Patent 2 154 449 describes the antifungal properties of C3 - CI2 carboxylic acids and salts thereof, in particular the incorporation of calcium propionate in bread dough in order to prevent the formation of mould on bread.
European Patent Application EP 0 244 144 A 1 teaches the addition of glyceryl fatty acid esters in combination with one or more C6.C,8 carboxylic acids as preservatives to, inter alia, food compositions.
International application WO 96/29895 describes a method for improving the shelf/storage life of perishable products by treating surfaces, equipment and materials, which come into contact with the products during the processing thereof, with an antimicrobial aromatic compound. 
WO 96/29895 states that fatty acids, including nonanoic acid, can also be used in combination with the aromatic compound.
International application WO 92/19104 teaches the use of C7 - C20 carboxylic acids, including nonanoic acid, for controlling infections in plants caused by bacteria and moulds. 
European Patent Application EP 0 022 289 relates to the incorporation of C3 - C, , carboxylic acids in polymers for the production of medical instruments, such as catheters.
European Patent Application EP 0 465 423 describes antimicrobial pharmaceutical preparations containing C4 - C,4 carboxylic acids. 
US Patent 4 406 884 describes antimicrobial pharmaceutical preparations for topical use which contain C5 - C,2 carboxylic acids.
US Patent 3 931 413 teaches the treatment of plants with C6 - C,8 carboxylic acids to combat infections by moulds which overwinter in the buds of the plants. 

Nonanoic acid is also used in some meat products to adjust the acidity. 

For instance, US Patent 4 495 208 describes a dog or cat food with good storage/shelf life which has a high moisture content (Aw > 0.9 and a water content of 50 - 80 %) that contains 4 -15 % (m/m) fructose, 0.3 - 3.0 % (m/m) of an edible organic acid, sufficient inorganic acid to obtain a pH in the range of 3.5 - 5.8 and an antifungal agent. 
The organic acid is preferably chosen from heptanoic acid, octanoic acid, nonanoic acid or a combination thereof.
In the animal feed according to US Patent 4 495 208 the edible organic acid is always present alongside a sugar (fructose) and an antifungal agent (antimycotic) known per se, such as sorbic acid and/or the salts thereof. 
It is stated that the combination of these three constituents in the indicated amounts gives a synergistic bactericidal action.
US Patent 3 985 904 describes a food based on meat which has a high moisture content and is suitable for human consumption or as an animal feed. 
This food has a moisture content of at least approximately 50 % (m m) and a water activity A,,, of at least approximately 0.90 and contains more than 50 % (m/m) of a ground, boiled, protein-like chicken, fish or meat material. 1 - 35 % (m m) of a gelatine-like filler based on starch, between 1.7 and 3.8 % of an edible, non-toxic acid and an effective amount of an antifungal agent.
The edible organic acid is incorporated in this food in an amount which is sufficient to bring the pH of the food to a value in the range from 3.9 to 5.5. 
Although US-A 3 985 904 mentions various suitable edible acids in column 6, nonanoic acid is not explicitly mentioned here.
According to US-A 3 985 904, the antifungal agent is chosen from benzoates, propionates and sorbate salts.
EP-A 0 876 768 describes the use of fatty acid monoesters of polyglycerol to improve the storage/shelf life of foods. 

Here the fatty acid radicals can be chosen from caproic acid, caprylic acid, lauric acid or myristic acid.
The use of nonanoic acid in herbicidal compositions for agricultural use is described, inter alia, in US Patents 5 098 467, 5 035 741, 5 106 410 and 5 975 4110. US Patents 4 820 438, 5 330 769 and 5 391 379 describe the use of nonanoic acid in soap and cleaning agents.
None of the above literature citations describes or suggests unambiguously that nonanoic acid can be safely incorporated in foods and/or can be used on foods in order to inhibit the growth of bacteria, moulds and yeasts. In particular, none of these literature citations teaches the dosage at which nonanoic acid can safely be used for this purpose.
Currently, natamycin is used as antifungal agent in cheese making. 

This compound, which is also designated pimaricin or "antibiotic A5283" and is marketed under the trade names Delvocid® and Natamax® (inter alia), is a metabolic product of Streptomyces natalensis and S. chattanoogensis.
However, the use of natamycin has a number of disadvantages. For instance it is fairly expensive. 
Moreover, it has been found that the mould Penicillium discolor is able to grow on (the surfaces of) cheeses treated with natamycin. 
This is particularly disadvantageous in the cheese industry, since P. discolor is widespread in cheese warehouses.
It has now been found that nonanoic acid displays an antimicrobial action, in particular an antifungal action, especially when it is used in amounts which can suitably be incorporated in food products. More particularly, it has been found that nonanoic acid can advantageously be used as an antimicrobial agent, in particular antifungal (fungicidal) agent, in dairy products such as cheese and products based on fruit, such as fruit juices.
The antimicrobial action of nonanoic acid found according to the invention is partly surprising because it is known that some types of mould (such as Aspergillus niger, Synchephalastrum racemosus, Geotrichum candidum, Penicillium expansum, Rhizopus stolonifer and Mucor plombus) naturally produce nonanoic acid. 
In addition, it has been found according to the invention that nonanoic acid is also able to inhibit the development of yeasts, which can likewise arise in cheese warehouses.
In a first aspect the invention therefore relates to the use of nonanoic acid (n-octane- 1 -carboxylic acid, pelargonic acid, n-nonylic acid) as an antimicrobial agent, in particular antifungal agent (additive) in or for foods and/or other products which have to be protected against perishing caused by microorganisms. 
The invention also relates to the use of salts of nonanoic acid as an antimicrobial agent.
The invention further relates to foods which contain nonanoic acid as an antimicrobial agent, in particular antifungal agent. 
The food can be any substance that is suitable for consumption by humans or animals, in particular for human consumption, and can be either a ready-to-eat food product or a constituent that can be incorporated in or processed to give a food product. The food or food product is in particular a product or substance that is susceptible to perishing caused by microorganisms, including bacteria, yeasts and in particular moulds (that is to say when no antimicrobial agent is added), such as, for example, a substance or product which will keep for between a few days and a few weeks (for example from 3 days to 3 weeks) under the customary conditions for storage of the product, such as a temperature in the range from room temperature (20 - 25 °C) down to refrigerator temperature (approximately 4 °C). However, the invention is not restricted to these.
In this context the nonanoic acid is used to inhibit microbial growth, in particular the formation of mould, and thus to extend the storage/shelf life. 
For instance, microbial growth can be retarded by the use of nonanoic acid. 
The degree of retardation will be dependent on, inter alia, the food, the nonanoic acid concentration, the conditions under which the food is stored (temperature, atmospheric humidity), the types of microorganisms to which the food is exposed and the degree of loading. 
In the case of mould formation, the mould formation (i.e. the point in time at which the first growth of mould is discernible to the naked eye) will in general be delayed by at least one day, preferably at least 5 - 7 days, that is to say at the temperature at which foods are usually stored - usually room temperature (20 °C) or in the refrigerator (4 °C) - compared with the untreated food. For instance, in the case of cheese that was coated with a nonanoic acid-containing coating according to the invention the first discernible formation of mould was postponed from 60 to 67 days. In this context reference is made to Example 1 below, as well as the results given in Figure 1. 
For the purposes of the invention, "inhibiting mould formation" and/or "antifungal" is preferably also understood to mean that the development of yeasts is (also) inhibited.
Moreover, it has been established according to the invention that nonanoic acid also has an antibacterial action, for example against bacteria which cause food to perish or otherwise reduce the quality thereof, and or against pathogens such as Listeria, Legionella, Salmonella and E.coli O157, Staphylococcus.
This inhibitory action of nonanoic acid on (the growth of) bacteria can also advantageously be employed in (the preparation of) fermented dairy products such as yoghurt. 
This will be explained in more detail below. The food can be a solid, semi-solid or fluid food and can be a fermented or non- fermented food.
A few non-limiting examples of foods in which nonanoic acid can be used according to the invention as an antimicrobial agent, in particular antifungal agent, are: - ready-to-eat food products, including dough products such as pre-baked bread, noodles, pasta, soups and the like; fish and meat products such as sausage, and products based on vegetables or fruit, such as fruit juices and canned fruit or combinations of fruit (juices) with dairy products; flour; nuts and (dried) southern fruits; and also products such as pre-prepared meals, diet foods, complete foods and baby food; foods and constituents for further processing, such as mayonnaise, ketchup and similar sauces; jam, marmalade and similar fruit preparations; and the like. According to the invention nonanoic acid can also be used outside the food sector as an antimicrobial agent, in particular antifungal and/or antibacterial agent, and examples of this will be given below.
One example that is worthy of mention at this juncture is the use of nonanoic acid or a nonanoic acid-containing coating to improve the storage/shelf life of fruit such as oranges, lemons, grapefruit, apples, pears and also nuts and (dried) southern fruits, coffee, tea, tobacco and the like, in particular before or during transport and/or during long-term storage, for example in a warehouse or a fruit store (which may or may not be air- conditioned).
When used as an antifungal agent according to the invention, the nonanoic acid will be used in an amount effective for the inhibition of moulds, yeasts and bacteria, which as a rule will be between 1 and 10,000 mg nonanoic acid per kg food, in particular 10-1,000 mg nonanoic acid per kg food and more particularly 100-500 mg nonanoic acid per kg food. 
Thus, for example, nonanoic acid can be used in yoghurt in an amount of approximately 200 milligram (mg) nonanoic acid per kilogram (kg) yoghurt. 
The lower limit for the effective amount of nonanoic acid will preferably be chosen from the series 10, 25, 50 or 100 mg nonanoic acid per kg food, whilst the upper limit is preferably chosen from the series 10,000, 5,000, 2,500, or 1,000 mg nonanoic acid per kg food.
Preferably, these amounts are based on the water content of the food. Thus, in the case of a food having a water content of 80 %, 80 % of the abovementioned amounts of nonanoic acid can also be added per kg food. The precise amount of nonanoic acid will, however, be dependent on the intended food and the way in which the nonanoic acid is used in the food. 

Thus, the nonanoic acid can be uniformly distributed throughout the entire food but, for example - especially in the case of solid or semi-solid foods - can also be present essentially only on or near the surface of the food, for example in the form of a nonanoic acid-containing antimicrobial, in particular antifungal, coating or surface layer, or as a result of treatment of the surface of the food with nonanoic acid. In these latter cases the concentration of nonanoic acid, based on the complete food, can be low (that is to say lower than the amounts indicated above), provided that sufficient nonanoic acid is present at or close to the surface in order to achieve the desired antimicrobial, in particular antifungal, action.
In general the presence of nonanoic acid in amounts of 10 - 10,000 ppm, in particular 100 - 2,000 ppm - i.e. locally or uniformly throughout the entire food - will be adequate to obtain the desired antimicrobial, in particular antifungal, action. The same concentrations of nonanoic acid - i.e. locally or uniformly throughout the entire food - will as a rule be sufficient to inhibit and/or to prevent the growth of yeast and/or of bacteria.
In a preferred aspect the food product is a dairy product, which in general is defined as a food based on milk or constituents of milk, in particular based on cows milk or constituents thereof. The dairy product is in particular a fermented dairy product that can be solid, semi- solid or fluid. 
A few non-limiting examples are cheese, butter, cream, yoghurt or yoghurt products (for example yoghurt drinks, such as, for example, milk/fruit juice drinks), cottage cheese, kefir, milk puddings and the like. 
The invention can also be employed in food products in which such dairy products have been incorporated/processed, such as sauces, pastries, desserts, foods (including complete food and baby food), snacks (for example containing cheese), meat products (such as ham in which proteins have been incorporated), powdered milk and coffee whiteners, and the like.
Use in cheese, and in particular in cheeses which have a low salt content (that is to say less than 4 %, in particular less than 3 %) and a high moisture content (that is to say 30 % or more, in particular 40 % or more) is to be particularly preferred. This can be carried out in particular by treating the surface of the cheese with nonanoic acid. 
Thus, the invention can (also) be used with feta, cheese spread and similar products.

The fermented dairy product preferably has a pH of 3.5 to 5.5, for example in the range of 5.1 - 5.5 for cheese and of 3.9 - 4.4 for yoghurt. 
Although it is not precluded that addition of nonanoic acid according to the invention makes some (usually minor) contribution to achieving this value, the final pH will as a rule be the result of the fermentation process and the buffer action possibly associated with this. 
In another preferred embodiment the food product is a fruit juice or similar drink, such as, for example, products in which dairy products such as milk or yoghurt and fruit juices have been processed, which have a limited shelf-life.
The nonanoic acid can be used in a manner known per se for antimicrobial agents, in particular antifungal agents, that is to say by adding the nonanoic acid or a nonanoic acid- containing additive to the food or food product, or incorporating the nonanoic acid or a nonanoic acid-containing additive in the food or food product, during and/or after the preparation thereof. During this operation the nonanoic acid can be uniformly mixed or distributed through the food and/or used on the surface of the food, for example by spraying or brushing with nonanoic acid (for example in the form of an aqueous solution), by immersing (in particular cheese) in a solution of nonanoic acid or by applying a nonanoic acid-containing coating. For this operation it is possible to use, for example, an aqueous solution or suspension of nonanoic acid or another nonanoic acid-containing, preferably liquid, mixture, which contains 100 - 5,000 ppm, in particular 200 to 3,000 ppm nonanoic acid and which furthermore can contain all constituents known per se for solutions for applying a cheese coating, such as (the constituents of) synthetic coatings known per se (for example based on copolymers) and/or coatings based on foodstuffs.
For instance - in a 140 gram coating for a 12.8 kg cheese - the nonanoic acid concentration in the coating can be 5,000 ppm (which corresponds to 49.2 mg nonanoic acid per kg cheese), 1,000 ppm (which corresponds to 9.8 mg/kg cheese) or 100 ppm (which corresponds to 0.98 mg/kg cheese).
The nonanoic acid-containing cheese coating thus obtained, the cheeses which have been provided with such nonanoic acid-containing cheese coatings and the nonanoic acid- containing solutions which are used in this operation form further aspects of the invention. 
In this context a further advantage of nonanoic acid is that it is also able to counteract and/or prevent too extensive development of the surface flora on the cheese (coating) - which can lead to the cheese rind being adversely affected - (this is in contrast to natamycin, that essentially is not able to exert any influence on bacterial growth).

As a rule the nonanoic acid will be used to replace the one or more antimicrobial, in particular antifungal, additives already used in a food known per se. 
In addition, the nonanoic acid can advantageously be used in those foods for which the known antimicrobial agents are unsuitable or less suitable. 
For such applications the use of nonanoic acid can form an alternative to the sterilisation treatments and/or similar antimicrobial treatment (that is to say other than the use of an antimicrobial additive) which are otherwise required.
Usually a single treatment of the food with nonanoic acid - such as the application of a nonanoic acid-containing coating - will be sufficient to obtain the desired antimicrobial action. However, repeated treatment of the food with nonanoic acid is not precluded. 
According to the invention nonanoic acid is used in particular to replace natamycin, in particular in applications in the dairy and cheese industries. In this regard reference is made, for example, to the applications of natamycin which are described by J. Stark in E>e Ware(n) Chemicus, 27 (1997), 173-176.
According to the invention nonanoic acid is highly preferentially compatible with the food, that is to say the use of nonanoic acid according to the invention has no adverse effect on the flavour, odour, consistency, pH or other desired characteristics of the food, at least not during the time that the food has to be or can be kept or stored prior to end use or consumption. 
As a rule this means that the food must be acid-resistant to a certain extent, that is to say at least must be able to withstand the pH that is obtained by the use of the nonanoic acid in the abovementioned amounts. In the event of possible problems with the compatibility, the use of a separate nonanoic acid-containing coating can offer a solution.
The food can furthermore contain all other additives known per se for the food, provided that these are compatible with nonanoic acid and do not adversely affect the antimicrobial action thereof. When nonanoic acid is used as antimicrobial agent according to the invention, as a rule no further antimicrobial agent will be required and according to one embodiment of the invention the food essentially contains exclusively nonanoic acid as antimicrobial agent, that is to say in the amounts specified above (in per cent by mass or ppm). 
However, it can not be entirely precluded that in addition to the nonanoic acid minor amounts of one or more further antimicrobial agents known per se are present, such as the agents which are mentioned below. Therefore, "essentially exclusively" is defined as meaning that the nonanoic acid makes up at least 80 % (m m), preferably at least 90 % (m/m) and more preferentially at least 95 - 99 % (m/m) of all antimicrobial constituents present (that is to say added to the food in order to achieve an antimicrobial action). 

Furthermore it is possible to use nonanoic acid in a mixture with one or more antimicrobial agents which are known per se and are compatible with nonanoic acid, a synergistic effect possibly being able to be obtained. In this case - compared with the use of the known agent as such - the nonanoic acid will as a rule replace some of the quantity of the known antimicrobial agent usually used. 

Nonanoic acid will as a rule make up at least 30 % (m/m), preferably at least 50 % (m/m) and more preferentially at least 70 % (m m) of the total antimicrobial constituents in such mixtures.
A few non-limiting examples of antimicrobial agents that can be used according to the invention in combination with nonanoic acid are: sorbic acid and salts thereof, benzoic acid and salts thereof, para-hydroxybenzoic acid or esters thereof, propionic acid and salts thereof, pimaricin, polyethylene glycol, ethylene/propylene oxides, sodium diacetate, caprylic acid (octanoic acid), ethyl formate, tylosin, polyphosphate, metabisulphite, nisin, subtilin and diethyl pyrocarbonate. 

The nonanoic acid can furthermore be used in combination with agents for adjusting the acidity, including the acids acceptable for foods, such as citric acid, acetic acid and the like. In this context the nonanoic acid can, in particular, protect the food (which in this case can have a pH in the range from 2 to 6) against acid-resistant moulds. Examples of such acid-resistant moulds are, but are not restricted to, Penicillium roqueforti, P. carneum, P. italicum, Monascus ruber and/or Paecilomyces variotii (which occur, for example, in rye bread); and Penicillium glandicola, Penicillium roqueforti, Aspergillus flavus, Aspergillus candidus and or Aspergillus terreus (which, for example, occur in products which have been preserved by acid, such as sour and/or sweet-sour preserves). More generally, according to the invention it is preferable that at least some, and preferably an appreciable proportion, of the nonanoic acid is present in the undissociated form in the food. 
The general rule in this context is that the amount of undissociated nonanoic acid increases at lower pH: for instance, approximately 90 % of the nonanoic acid is present in undissociated form at a pH of approximately 3.8.
According to one aspect of the invention, nonanoic acid is therefore also used in foods which have a low pH, such as a pH in the range 2 to 6, preferably 3 to 5.8, or 4 to 5.6. 
For instance, for example, the pH of cheese rind is around 4.8 - 5.3.
In addition to the antimicrobial, in particular antifungal, action described above, the use of nonanoic acid according to the invention can also yield the following further advantages: nonanoic acid is a stable molecule in both the dissociated and undissociated form.
The long alkyl chain is inert and renders the molecule barely reactive. nonanoic acid is a natural substance which occurs in plants, inter alia; - nonanoic acid has been approved for use in foods (inter alia by the FDA); nonanoic acid remains stable under the majority of processing steps/processes for food products; nonanoic acid is less susceptible to UV light than is, for example, natamycin; nonanoic acid is stable in the presence of metals in metallic form; - nonanoic acid is stable under heating.
The invention has been described above with reference to a preferred embodiment thereof; that is to say use in foods, in particular in dairy products. 
However, it will be clear to those skilled in the art from the above description that nonanoic acid can also find use outside the food sector as an antifungal, yeast-inhibiting and/or antibacterial agent. In this context it will, in particular, be an advantage that nonanoic acid has been approved for use in foods, so that it can be used in applications where it can come into contact with foods or the human body, such as with the skin.
A number of possible, non-limiting applications are: use as or in disinfectant(s), cleaning agent(s) and the like, for both domestic and industrial applications; disinfection and/or cleaning (including preventive treatment) of conveyor belts, pallets and the like; disinfection and/or cleaning (including preventive treatment) of apparatus, products and/or surfaces which come into contact with foods, such as cutting machines, mixers, stirrers, sorting equipment, filling machines and other equipment from the food processing industry; vats, dishes, tanks, plates, containers and other holders; and also worktops, sink units and the like; both domestic and industrial; disinfection and/or cleaning (including preventive treatment) of areas which may or may not be enclosed, in particular areas in which food products are processed and/or stored, such as cupboards, refrigerators, kitchens, factory areas, freight areas, warehouses and the like (both domestic and industrial); and in particular cheese warehouses and other commercial premises where P. discolor can occur; coating and/or (preventive) treatment of packaging for, for example, foods (such as fruit, vegetables, cheese and the like), for example made of materials such as plastic, paper, cardboard or shaped cardboard; protection of fruit, such as oranges, lemons, grapefruit, apples, pears; nuts and
(dried) southern fruits, coffee, tea, tobacco and the like, and also of cut flowers and bulbs, against moulds and/or bacteria, before or during transport and/or during (long- term) storage, for example in a warehouse or in an (optionally) air-conditioned fruit store; disinfection and/or cleaning (including preventive treatment) of, for example, tents or tarpaulins, and also indoors (for example on walls) to prevent or to counteract mould growth, for example as a consequence of damp; protection and/or treatment of wood and similar materials; use in cosmetics and skincare products; use for pharmaceutical applications, for example to prevent and treat fungal infections and yeast infections, such as Candida. These aspects of the invention in general comprise the treatment of a surface or substrate that is susceptible to mould formation, or that can be contaminated or infected by a mould and/or the spores thereof, with an amount of nonanoic acid which has an effective antifungal and/or antibacterial action.
This amount will differ depending on the application and the way in which the nonanoic acid is used on the surface or substrate. 
As a rule the presence of nonanoic acid in amounts of 10 - 10,000 ppm, in particular 100 - 2,000 ppm, will again be sufficient to achieve an antimicrobial, in particular antifungal, action, although higher concentrations can be used for some applications. The nonanoic acid can be used on the surface or substrate in any suitable way, such as, once again, spraying or brushing with nonanoic acid (for example in the form of an aqueous solution), by applying a nonanoic acid-containing coating or by use of an atomised spray containing nonanoic acid. 
This treatment can optionally be repeated.
In this context the nonanoic acid can once again be used instead of, or together with, disinfectants which may be known for the envisaged application, as well as in combination with other agents or constituents customary for the envisaged application. For these applications, the nonanoic acid and any other constituents can optionally be marketed in a suitable container, for example in a bottle or in the form of a spray.
A particular application of nonanoic acid according to the invention furthermore relates to the control - in particular the inhibition - of bacterial growth during fermentation processes, such as the preparation of fermented food products such as yoghurt. For this application use is made in particular of the antibacterial action of nonanoic acid. For instance, nonanoic acid can be used to control the pH during or after such fermentation processes and in particular to prevent and/or reduce post-acidification of, for example, yoghurt, as explained in more detail in the examples. 
The taste of the yoghurt is retained for longer as a result. 
In addition, the antimicrobial, in particular antifungal, action according to the invention will also be obtained.
The invention will now be explained with reference to the following non-limiting examples and the figures, in which:
Figure 1 is a graph (time against visible intensity of mould formation) in which the effect of nonanoic acid on mould formation on Gouda cheese is shown; Figure 2 is a graph (time against number of bacteria) which shows the effect of nonanoic acid (pelargonic acid) on the development of yoghurt bacteria at 7 °C; - 
Figure 3 is a graph (time against pH) which shows the effect of nonanoic acid (pelargonic acid) on the post-acidification of yoghurt at 7 °C; Figure 4 is a graph (time against number of bacteria) which shows the effect of nonanoic acid (pelargonic acid) on the development of yoghurt bacteria at 32 °C; Figure 5 is a graph (time against pH) which shows the effect of nonanoic acid (pelargonic acid) on the post-acidification of yoghurt at 32 °C;
Figure 6 is a plot (time against number of bacteria) that shows the influence of nonanoic acid (pelargonic acid) on the development of surface flora on cheese rind; Figure 7 is a plot (time against number) that shows the effect of nonanoic acid (pelargonic acid) on the development of D. hansenii, S. cereviseae, C. lipolytica and R. rubra;
Figures 8 A and 8B are photographs which show the effect of natamycin (Figure 8 A) and nonanoic acid (Figure 8B), respectively, on the inhibition of the growth of P. discolor on blocks of cheese rind;
Figure 9 is a graph (time against number of bacteria) which shows the effect of nonanoic acid on the growth of Bacillus cereus in soup;
Figure 10 is a graph (time against number of bacteria) which shows the effect of nonanoic acid on the growth of Staphylococcus aureus in soup;
Figure 11 is a graph (time against number of cells) which shows the effect of nonanoic acid on the growth of Debaromyces hansenii in a milk/fruit juice drink; Figure 2 is a graph (time against number of cells) which shows the effect of nonanoic acid on the growth of Penicillium italicum in a milk/fruit juice drink.

Experimental
Example 1 : Use of nonanoic acid in Gouda cheese
A trial production of Gouda cheeses was made. In this batch of cheeses one series was treated with 1000 ppm nonanoic acid (nonanoic acid) and the other series was not treated with a fungicide (blank). The two series were inoculated with spores of the mould P. discolor (0.1 spore/cm2) and stored at 13 °C and 88 % relative humidity. All individual cheeses were assessed visually at frequent intervals for the extent of the presence of mould. The following scale was used for the optical assessment of the intensity of visible moulds;
0 = no mould 1 = some mould
2 = distinct mould
3 = considerable mould
4 = very considerable mould or overgrown with mould.
The results are shown diagrammatically in Figure 1. In the case of the cheeses without fungicide slight mould growth (intensity 1) was detectable after about 60 days. 
In the case of the series of cheeses treated with nonanoic acid it was 66 days before mould growth (intensity 1) was observed.
Example 2: Use of nonanoic acid in yoghurt to prevent post-acidification In an experiment various concentrations of nonanoic acid were added to freshly prepared yoghurt. 
One series was monitored for 8 hours at the culture temperature (filling, 32 °C) and another series was incubated for 14 days at 7 °C (refrigerator temperature). 
This was carried out to investigate the extent to which nonanoic acid has an effect during yoghurt fermentation and/or during storage of the filled packs of yoghurt. 
For both series the pH was determined and the number of yoghurt bacteria.
The results are shown in Figures 2 - 5. Addition of 1,000 ppm nonanoic acid substantially prevented post-acidification (32 °C) and the number of yoghurt bacteria was reduced by 2 log units. At 7 °C an effect on the post-acidification was already detectable at lower nonanoic acid contents (200 ppm). Addition of 1,000 ppm prevented post- acidification Virtually completely when storing at refrigerator temperature and the number of yoghurt bacteria decreased by 4 log units.
Example 3: Effect of nonanoic acid on the surface flora of cheese rind
The effect of nonanoic acid on the surface flora on cheese rind was determined. 
The results (time against number of bacteria) are shown in Figure 6.
The effect of nonanoic acid (pelargonic acid) on the development of D. hansenii, S. cereviseae, C. lipolytica and R. rubra was also determined. 
The results (time against number) are shown in Figure 7.
Example 4: Use on blocks of cheese rind
In this experiment blocks of cheese rind were inoculated with P. discolor. The blocks were incubated at 20 °C and high relative humidity (95 %). These conditions were employed to provide the mould with the optimum opportunity to grow and are therefore more severe than the usual conditions for maturing cheese.
The results are given in Figure 8, which shows photographs of the blocks of cheese rind taken two weeks after inoculating with P. discolor. 
One series was treated with natamycin (Figure 8A) and the other series with nonanoic acid (Figure 8B). 
It can clearly be seen that after 2 weeks mould formation was inhibited in the blocks treated with nonanoic acid.
Example 5: Use in soup
In this experiment a creamy mushroom soup with parsley (chill-fresh product obtained from the Albert Heijn delicatessen in March 2000) was inoculated with
104 CFU/ml (colony-forming units per ml soup) of Bacillus cereus (NIZO B443) or with 104 CFU/ml Staphylococcus aureus (NIZO B1211). 
The soup was then incubated at 20 °C, without and with increasing concentrations of nonanoic acid (100, 500 and 1,000 ppm). 
Samples were taken at the times indicated in Figures 9 and 10 (Figure 9 for B. cereus and Figure 10 for S. aureus). 
From each sample a series of dilutions was plated to determine the number of CFU/ml soup. 

The B. cereus samples were plated on mannitol egg yolk polymyxin agar (MYP) and incubated for 24 hours at 30 °C; the S. aureus samples were plated on Baird-Parker egg yolk tellurite agar (BP) and incubated for 48 hours at 37 °C. The results are shown in Figures 9 and 10. The addition of 100 ppm nonanoic acid to the soup has a slightly inhibiting effect on the growth of both B. cereus and S. aureus, whilst with the addition of 500 or 1,000 ppm nonanoic acid the growth of both bacteria is virtually completely inhibited. Example 6: Use in a milk/fruit juice product
In this experiment a milk/fruit juice drink ("Milk & Fruit"™ from Coberco, obtained from Albert Heijn; "Milk & Fruit"™ is a chilled-fresh, pasteurised product without preservatives, consisting of 80 % drinking yoghurt and 20 % pineapple juice and has a pH value of 4.0) was inoculated with 102 CFU/ml Debaromyces hansenii (NIZO F937) or Penicillium italicum (CBS 278.58). 
The milk/fruit juice drink was then incubated at 20 °C, without and with increasing concentrations of nonanoic acid (100, 500 and 1,000 ppm). 
Samples were taken at the times indicated in Figures 11 and 12 (Figure 11 for D. hansenii and Figure 12 for P. italicum). 
For each sample a series of dilutions was plated in order to determine the number of CFU/ml drink. 
The samples were plated on oxytetracycline glucose yeast agar (OGY) and incubated for 5 days at 25 °C. 
The results are shown in Figures 11 and 12. Addition of 100 ppm nonanoic acid gives complete inhibition of the growth of D. hansenii. 
Addition of 100 or 500 ppm inhibits the growth of P. italicum and addition of 1,000 ppm nonanoic acid gives complete inhibition of the growth of P. italicum for up to 6 days.

GENERAL DESCRIPTION OF CARBOXYLIC ACID
Carboxylic acid is an organic compound whose molecules contain carboxyl group and have the condensed chemical formula R-C(=O)-OH in which a carbon atom is bonded to an oxygen atom by a solid bond and to a hydroxyl group by a single bond), where R is a hydrogen atom, an alkyl group, or an aryl group. Carboxylic acids can be synthesized if aldehyde is oxidized. Aldehyde can be obtained by oxidation of primary alcohol. Accordingly, carboxylic acid can be obtained by complete oxidation of primary alcohol. A variety of Carboxylic acids are abundant in nature and many carboxylic acids have their own trivial names. Examples are shown in table. In substitutive nomenclature, their names are formed by adding -oic acid' as the suffix to the name of the parent compound. The first character of carboxylic acid is acidity due to dissociation into H+ cations and RCOO- anions in aqueous solution. The two oxygen atoms are electronegatively charged and the hydrogen of a carboxyl group can be easily removed. The presence of electronegative groups next to the carboxylic group increases the acidity. For example, trichloroacetic acid is a stronger acid than acetic acid. Carboxylic acid is useful as a parent material to prepare many chemical derivatives due to the weak acidity of the hydroxyl hydrogen or due to the difference in electronegativity between carbon and oxygen. The easy dissociation of the hydroxyl oxygen-hydrogen provide reactions to form an ester with an alcohol and to form a water-soluble salt with an alkali. Almost infinite esters are formed through condensation reaction called esterification between carboxylic acid and alcohol, which produces water. The second reaction theory is the addition of electrons to the electron-deficient carbon atom of the carboxyl group. One more theory is decarboxylation (removal of carbon dioxide form carboxyl group). Carboxylic acids are used to synthesize acyl halides and acid anhydrides which are generally not target compounds. They are used as intermediates for the synthesis esters and amides, important derivatives from carboxylic acid in biochemistry as well as in industrial fields. There are almost infinite esters obtained from carboxylic acids. Esters are formed by removal of water from an acid and an alcohol. Carboxylic acid esters are used as in a variety of direct and indirect applications. Lower chain esters are used as flavouring base materials, plasticizers, solvent carriers and coupling agents. Higher chain compounds are used as components in metalworking fluids, surfactants, lubricants, detergents, oiling agents, emulsifiers, wetting agents textile treatments and emollients, They are also used as intermediates for the manufacture of a variety of target compounds. The almost infinite esters provide a wide range of viscosity, specific gravity, vapor pressure, boiling point, and other physical and chemical properties for the proper application selections. Amides are formed from the reaction of a carboxylic acids with an amine. Carboxylic acid's reaction to link amino acids is wide in nature to form proteins (amide), the principal constituents of the protoplasm of all cells. Polyamide is a polymer containing repeated amide groups such as various kinds of nylon and polyacrylamides. Carboxylic acid are in our lives.
ALIPHATIC CARBOXYLIC ACIDS

COMMON NAME

SYSTEMATIC NAME
CAS RN
FORMULA
MELTING POINT


Formic Acid    Methanoic acid    64-18-6    HCOOH
8.5 C


Acetic Acid    Ethanoic acid    64-19-7    CH3COOH    
16.5 C

Carboxyethane    Propionic Acid    79-09-4    CH3CH2COOH    
-21.5 C

Butyric Acid    n-Butanoic acid    107-92-6    CH3(CH2)2COOH    
-8 C

Valeric Acid    n-Pentanoic Acid    109-52-4    CH3(CH2)3COOH    
-19 C

Caproic Acid    n-Hexanoic Acid    142-62-1    CH3(CH2)4COOH    
-3 C

Enanthoic Acid    n-Heptanoic acid    111-14-8    CH3(CH2)5COOH    
-10.5 C

Caprylic Acid    n-Octanoic Acid    124-07-2    CH3(CH2)6COOH    
16 C

alpha-Ethylcaproic Acid    2-Ethylhexanoic Acid    149-57-5    CH3(CH2)3CH(C2H5)COOH    
-59 C

Valproic Acid    2-Propylpentanoic Acid    99-66-1    (CH3CH2CH2)2CHCOOH    
120 C

Pelargonic Acid    n-Nonanoic Acid    112-05-0    CH3(CH2)7COOH    
48 C

Capric Acid    n-Decanoic Acid    334-48-5    CH3(CH2)8COOH    
31 C


Nonanoic acid is a fatty acid which occurs naturally as esters are the oil of pelargonium. Synthetic esters, such as methyl nonanoate, are used as flavorings. Pelargonic acid is an organic compound composed of a nine-carbon chain terminating in a carboxylic acid. It is an oily liquid with an unpleasant, rancid odor. It is nearly insoluble in water, but well soluble in chloroform and ether.


Nonanoic acid, also called pelargonic acid, is an organic compound with structural formula CH3(CH2)7CO2H. It is a nine-carbon fatty acid. Nonanoic acid is a colorless oily liquid with an unpleasant, rancid odor. It is nearly insoluble in water, but very soluble in organic solvents. The esters and salts of nonanoic acid are called nonanoates. Its refractive index is 1.4322. Its critical point is at 712 K (439 °C) and 2.35 MPa.


 

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