MILK ACID

Milk acid, is an organic acid with applications in beer production as well as the cosmetic, pharmaceutical, food and chemical industries.
Milk acid is commonly used as a preservative and antioxidant.
Milk acid also has uses as a fuel additive, chemical intermediate, acidity regulator, and disinfectant.

CAS Number: 50-21-5
EC Number: 200-018-0
Molecular Formula: C3H6O3
Molar Mass: 90.078 g·mol−1

Milk acid was discovered in 1780 by Swedish chemist, Carl Wilhelm Scheele, who isolated the Milk acid from sour milk as an impure brown syrup and gave Milk acid a name based on its origins: 'Mjölksyra'.
The French scientist Frémy produced Milk acid by fermentation and this gave rise to industrial production in 1881.

Milk acid is produced by the fermentation of sugar and water or by chemical process and is commercially usually sold as a liquid.
Pure and anhydrous racemic Milk acid is a white crystalline solid with a low melting point.

Milk acid has two optical forms, L(+) and D(-).
L(+)-Milk acid is the biological isomer as Milk acid is naturally present in the human body.

Milk acid can be produced naturally or synthetically.
Commercial Milk acid is produced naturally by fermentation of carbohydrates such as glucose, sucrose, or lactose.

Wih the addition of lime or chalk, the raw materials are fermented in a fermenter and crude calcium lactate is formed.
The gypsum is separated from the crude calcium lactate, which results in crude Milk acid.
The crude Milk acid is purified and concentrated and L(+) Milk acid is the result.

One specific use of Milk acid is in I.V solutions, where Milk acid is an electrolyte to help replenish the bodies fluids.
Milk acid is also used in dialysis solutions, which results in a lower incidence of side effects compared to Sodium Acetate which can also be used.

Milk acid comes in both R (D-) and S (L+) enantiomers which can be manufactured individually to near perfect optical purity.
This means Milk acid is great in the production of other products which require a specific stereochemistry.

Milk acid is used frequently in the cosmetic industry due to the effect of promoting collagen production, helping to firm the skin against wrinkles and sagging.
Milk acid can also cause micro peeling, which can help reduce various scars and age spots.

Milk acid is a great solution for people with sensitive or dry skin where exfoliants don’t work.
Milk acid is used as a food preservative, curing agent, and flavoring agent.

Milk acid is an ingredient in processed foods and is used as a decontaminant during meat processing.
Milk acid is produced commercially by fermentation of carbohydrates such as glucose, sucrose, or lactose, or by chemical synthesis.

Milk acid, also named ‘Lactic acid’, is an organic acid with the following chemicalformula: CH3CH(OH)CO2H.
The ofﬁcial name given by the International Union ofPure and Applied Chemistry (IUPAC) is 2-hydroxypropanoic acid.

Milk acid can be naturally produced, but Milk acid importanceis correlated with synthetic productions.
Pure Milk acid is a colourless andhydroscopic liquid; Milk acid can be deﬁned a weak acid because of Milk acid partial dissociationin water and the correlated acid dissociation constant (Ka= 1.38 10−4).

Milk acid is a chiral compound with a carbon chain composed of a central (chiral) atomand two terminal carbon atoms.
A hydroxyl group is attached to the chiral carbon atom while oneof the terminal carbon atoms is part of the carboxylic group and the other atom is part of the methylgroup.

Consequently, two optically active isomeric forms of Milk acid exist: L(+) form, alsonamed (S)-Milk acid, and D(−) form, or (R)-Milk acid.
L(+)-Milk acid is the biological isomer.

Antibacterial mechanism of Milk acid on physiological and morphological properties of Salmonella Enteritidis, Escherichia coli and Listeria monocytogenes:
Pathogens could be completely inactivated after exposure to Milk acid.
Milk acid resulted in great leakage of protein of three pathogens.

Bacterial protein bands of Milk acid-treated cells got fainter or disappeared.
Z-Average sizes of pathogens were changed to smaller after Milk acid treatment.
Milk acid caused collapsed or even broken cells with obvious pits and gaps.

Milk acid is widely used to inhibit the growth of important microbial pathogens, but Milk acid antibacterial mechanism is not yet fully understood.
The objective of this study was to investigate the antibacterial mechanism of Milk acid on Salmonella Enteritidis, Escherichia coli and Listeria monocytogenes by size measurement, TEM, and SDS-PAGE analysis.

The results indicated that 0.5% Milk acid could completely inhibit the growth of Salmonella Enteritidis, E. coli and L. monocytogenes cells.
Meanwhile, Milk acid resulted in leakage of proteins of Salmonella, E. coli and Listeria cells, and the amount of leakage after 6 h exposure were up to 11.36, 11.76 and 16.29 μg/mL, respectively.

Fifty strains each of Staphylococcus aureus, beta haemolytic Streptococci, Proteus species, Esch coli and Pseudomonas aeruginosa were subjected to 2%, 1 % and 0. 1 % Milk acid in peptorie water.
Minimum inhibitory concentration of Milk acid for all the strains of each of these organisms was 0.1% or 1%.

Depending upon Milk acids concentration, Milk acid added to peptone water brings down the PH to 2.5-4 which by itself has some inhibitory effect on the microorganisms.
Milk acid however, retains Milk acid inhibitory effect even if the Ph of the peptone water is brought back to 7.3.

Milk acid is a nontoxic and non-sensitizing agent because Milk acid is a normal metabolite of the body.
Thus, Milk acid can be used as a safe and effective antibacterial agent for local application.

Milk acid is a normal intermediate in the fermentation (oxidation, metabolism) of sugar.
Milk acid is concentrated form is used internally to prevent gastrointestinal fermentation.
Milk acid is conversion to glucose via gluconeogenesis in the liver and release back into the circulation

Milk acid is an organic acid occurring naturally in the human body and in fermented foods.
Milk acid is used in a wide range of food, beverages, personal care, healthcare, cleaners, feed & pet food and chemical products as a mild acidity regulator with flavour enhancing and antibacterial properties.

The commercial production of Milk acid is typically done by fermentation.
Because the L(+) form is preferred for Milk acid better metabolisation, Jungbunzlauer has chosen to produce pure L(+)-Milk acid by traditional fermentation of natural carbohydrates.

L(+)-Milk acid is a colourless to yellowish, nearly odourless, syrupy liquid with a mild acid taste.
Milk acid is commercially available as aqueous solutions of various concentrations.

These solutions are stable under normal storage conditions.
Milk acid is non-toxic to humans and the environment, but concentrated solutions of Milk acid can cause skin irritation and eye damage.
Milk acid is readily biodegradable.

Due to the high hygroscopicity of Milk acid, Milk acid concentrated aqueous solutions are usually used - syrupy, colorless, odorless liquids.
Oxidation of Milk acid is usually accompanied by decomposition.

Under the action of HNO 3 or O 2 of air in the presence of Cu or Fe, HCOOH, CH 3 COOH, (COOH) 2 , CH 3 CHO, CO 2 and pyruvic acid are formed.
Reduction of Milk acid HI leads to propionic acid, and reduction in the presence of Re-mobile leads to propylene glycol.

Milk acid dehydrates to acrylic acid, when heated with HBr, forms 2-bromopropionic acid, when the Ca salt reacts with PCl 5 or SOCl 2 -2-chloropropionyl chloride.
In the presence of mineral acids, self-esterification of Milk acid occurs with the formation of lactone, as well as linear polyesters.

When Milk acid interacts with alcohols, hydroxy acids RCH 2 CH (OH) COOH are formed, and when Milk acid salts react with alcohol esters.
The salts and esters of Milk acid are called lactates.

Milk acid is formed as a result of Milk acid fermentation (with sour milk, sauerkraut, pickling vegetables, ripening cheese, ensiling feed); D- Milk acid is found in tissues of animals, plants, and also in microorganisms.
In industry, Milk acid is obtained by hydrolysis of 2-chloropropionic acid and Milk acid salts (100 ° C) or lactonitrile CH 3 CH (OH) CN (100 ° C, H 2 SO 4 ), followed by the formation of esters, the isolation and hydrolysis of which leads to a high quality.
Other methods of producing Milk acid are known: the oxidation of propylene with nitrogen oxides (15-20 ° C) followed by treatment with H 2 SO 4 , the interaction of CH 3 CHO with CO (200 ° C, 20 MPa).

Milk acid is used in the food industry, in mordant dyeing, in leather production, in fermentation shops as a bactericidal agent, for the production of medicines, plasticizers.
Ethyl and butyl lactates are used as solvents for cellulose ethers, drying oils, vegetable oils; butyl lactate - as well as a solvent for some synthetic polymers.

Milk acid is an organic acid.
Milk acid has a molecular formula CH3CH(OH)COOH.

Milk acid is white in the solid state and Milk acid is miscible with water.
When in the dissolved state, Milk acid forms a colorless solution.

Production includes both artificial synthesis as well as natural sources.
Milk acid is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group.

Milk acid is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries.
The conjugate base of Milk acid is called lactate.

In solution, Milk acid can ionize, producing the lactate ion CH3CH(OH)CO−2.
Compared to acetic acid, Milk acids pKa is 1 unit less, meaning Milk acid is ten times more acidic than acetic acid.
This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group.

Milk acid is chiral, consisting of two enantiomers.
One is known as l-(+)-Milk acid or (S)-Milk acid and the other, Milk acid mirror image, is d-(−)-Milk acid or (R)-Milk acid.

A mixture of the two in equal amounts is called dl-Milk acid, or racemic Milk acid.
Milk acid is hygroscopic.

dl-Milk acid is miscible with water and with ethanol above Milk acid melting point, which is around 16, 17 or 18 °C.
d-Milk acid and l-Milk acid have a higher melting point.

Milk acid produced by fermentation of milk is often racemic, although certain species of bacteria produce solely (R)-Milk acid.
On the other hand, Milk acid produced by anaerobic respiration in animal muscles has the (S) configuration and is sometimes called "sarcolactic" acid, from the Greek "sarx" for flesh.

In animals, l-lactate is constantly produced from pyruvate via the enzyme lactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise.
Milk acid does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including monocarboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues.

The concentration of blood lactate is usually 1–2 mM at rest, but can rise to over 20 mM during intense exertion and as high as 25 mM afterward.
In addition to other biological roles, l-Milk acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA1), which is a Gi/o-coupled G protein-coupled receptor (GPCR).

In industry, Milk acid fermentation is performed by Milk acid bacteria, which convert simple carbohydrates such as glucose, sucrose, or galactose to Milk acid.
These bacteria can also grow in the mouth; the acid they produce is responsible for the tooth decay known as caries.

In medicine, lactate is one of the main components of lactated Ringer's solution and Hartmann's solution.
These intravenous fluids consist of sodium and potassium cations along with lactate and chloride anions in solution with distilled water, generally in concentrations isotonic with human blood.
Milk acid is most commonly used for fluid resuscitation after blood loss due to trauma, surgery, or burns.

Milk acid is a hydroxycarboxylic acid CH3CH(OH)COOH with two stereoisomers (D(-) and L(+)) and Milk acid has several applications in food, chemical, pharmaceutical and health care industries.
Milk acid is primarily used for food and pharmaceutical applications, preferentially the L(+) isomer, since Milk acid is the only Milk acid isomer produced in the human body.

Around 20 to 30% of the Milk acid production is used to obtain biopolymers (polyMilk acid).
Other uses of Milk acid include fibers and green solvents.

Milk acid is fully commercially available and largely (90%) produced by bacteria through anaerobic fermentation of sugars.
Milk acid can also be commercially produced by chemical synthesis.

The chemical production pathway gives an optical inactive racemic mixture (with the same quantity of L and D isomers), while the anaerobic fermentation pathway mostly yieldsone of the two stereoisomers, depending on the microorganism chosen.
The biotechnological option is widely available due to Milk acid renewable origin.
Milk acid can be produced via fermentation of sugars from different biomass, such as: starch crops, sugar crops, lignocellulosic materials and also from whey (a residue from cheese production).

The bulk of world production is based on homoplastic fermentation of sugars (from starch or sugar crops) where Milk acid is produced as sole product.
Conventional production systems require the addition of calcium hydroxide to control the fermentation pH.

This procedure results in calcium lactate as final product.
Several steps are required to ultimately obtain and purify Milk acid: filtration, acidification, carbon adsorption, evaporation, esterification, hydrolysis and distillation.

The conventional process is associated with high costs (due to the complex purification procedure) and poor environmental performance due to the production of large amounts of chemical effluents (e.g. calcium sulphate).
New separation technologies are being developed, such as bipolar electrodialysis with promising results.

Milk acid, the most fundamental natural ingredient in the dairy industry
In dairy products, Milk acid is one of the most common ingredients.

Milk acids purpose is generally as an acid regulator and in terms of flavouring.
The slightly sour taste observed in yogurts, cheeses and other milk products is generally the result of fermentation from Milk acid.

The signature flavour of sourdough bread is also a result of Milk acid during the baking process.
With the addition of this versatile supplement, the product can be acidified with ease to reach proper pH levels, while leaving the natural flavours undisturbed.

Milk acid, DL- is the racemic isomer of Milk acid, the biologically active isoform in humans.
Milk acid or lactate is produced during fermentation from pyruvate by lactate dehydrogenase.
This reaction, in addition to producing Milk acid, also produces nicotinamide adenine dinucleotide (NAD) that is then used in glycolysis to produce energy source adenosine triphosphate (ATP).

Milk acid appears as a colorless to yellow odorless syrupy liquid.
Corrosive to metals and tissue.
Used to make cultured dairy products, as a food preservative, and to make chemicals.

A normal intermediate in the fermentation (oxidation, metabolism) of sugar.
The concentrated form is used internally to prevent gastrointestinal fermentation.

Sodium lactate is the sodium salt of Milk acid, and has a mild saline taste.
Milk acid is produced by fermentation of a sugar source, such as corn or beets, and then, by neutralizing the resulting Milk acid to create a compound having the formula NaC3H5O3.
Milk acid was one of active ingredients in Phexxi, a non-hormonal contraceptive agent that was approved by the FDA on May 2020.

Milk acid (chemically, alpha or 2-Hydroxypropionic acid) takes roles in metabolic processes in the body; in red blood and in skeletal muscle tissues as a product of glucose and glycogen metabolism.
Milk acid is an "alpha hydroxy acid: which has a hydroxyl group on the carbon atom next to the acid group.

If the hydroxy group is on the second carbon next to the acid group, Milk acid is called beta-hydroxy acid.
Milk acid is converted in vivo to pyruvic acid (an alpha keto acid) which occurs as an intermediate product in carbohydrate and protein metabolism in the body.

Milk acid occurs as two optical isomers since the central carbon atom is bound to four different groups; a dextro and a levo form ( or an inactive racemic mixture of the two); only the levo form takes part in animal metabolism. Milk acid is present in sour milk and dairy products such as cheese, yogurt, and koumiss, leban, wines.
Milk acid causes tooth decay since Milk acid bacteria operates in the mouth.

Although Milk acid can be prepared by chemical synthesis, production of Milk acid by fermentation of glucose and other sugar substances in the presence of alkaline such as lime or calcium carbonate is a less expensive method.
The six-carbon glucose molecule is broken down to two molecules of the three-carbon compounds (Milk acid), during this anaerobic condition.

Synthetic Milk acid is used commercially in tanning leather and dyeing wool; as a flavouring agent and preservative in food processing and carbonated beverages; and as a raw material in making plastics, solvents, inks, and lacquers; as a catalyst in numerous chemical processes.
Milk acid is available as aqueous solutions of various concentrations, usually 22 - 85 percent (pure Milk acid is a colourless, crystalline substance.)

Although Milk acid is usually associated with milk and dairy products, Milk acid can also be found in many other fermented food products, including confectionery products, jams, frozen desserts, and pickled vegetables.
Milk acid bacteria (LAB) are heterogenous group of bacteria which plays a significant role in a variety of fermentation processes.

They ferment food carbohydrates and produce Milk acid as the main product of fermentation.
In addition, degradation of proteins and lipids and production of various alcohols, aldehydes, acids, esters and sulphur compounds contribute to the specific flavour development in different fermented food products.

The main application of LAB is as starter cultures, with an enormous variety of fermented dairy (ie. cheese, yoghurt, fermented milks), meat, fish, fruit, vegetable and cereal products.
Besides, they contribute to the flavour, texture and nutritional value of the fermented foods, and thus they are used as adjunct cultures.

Acceleration of cheese maturation, enhancement of yoghurt texture with the production of exo polysaccharides and control of secondary fermentations in the production of wine are some examples.
The production of bacteriocins and antifungal compounds has lead to the application of bio-protective cultures in certain foods.
Moreover, the well-documented health-promoting properties of certain LAB have lead to the addition of selected strains, in combination with bifidobacteria, as probiotic cultures with various applications in food industry.

Milk acid is an organic acid generated by microbial fermentation.
Several studies have tested a 2% concentration of Milk acid as a sanitizer, either by itself or in combination with a surface-active agent.

Milk acid–based sanitizers interfere with cell membrane permeability and cell functions such as nutrient transport.
These sanitizers are very promising and research is ongoing regarding their uses.

For example, in a recent study, ten commercially available sanitizers were tested for their effectiveness against Listeria monocytogenes on high-density polyethylene cutting boards.
Of all the products tested, which included QACs and sodium hypochlorite, a lactic-based sanitizer was the most effective against biofilm cells.

Milk acid is used since 1990s as a fine chemical (production 60 000–80 000 tons yr−1).
A major share (25 000 tons yr−1) is used as additive in the food industry.

The second main application is as building block for green polymers, solvents, and plasticizers.
Milk acid is chemically produced by hydrocyanation followed by hydrolysis of the cyanohydrin.

The main drawbacks are the manipulation of hydrogen cyanide (HCN), the production of (NH4)2SO4 (1 eq), and the complex purification steps to obtain food-grade Milk acid because the racemic acid is obtained.
To overcome these difficulties, the anaerobic fermentation from carbohydrates using Lactobacillus delbrueckii is a good alternative because only (S)-Milk acid is obtained in only one step.
The fermentation is performed at 50 °C over 2–8 days with a yield of 85–95% and the product concentration is 100 g l−1.

Milk acid bacteria (LAB) play an important role in food, agricultural, and clinical applications.
The general description of the bacteria included in the group is gram-positive, nonsporing, nonrespiring cocci or rods, which produce Milk acid as the major end product during the fermentation of carbohydrates.

The common agreement is that there is a core group consisting of four genera; Lactobacillus, Leuconostoc, Pediococcus and Streptococcus.
Recent taxonomic revisions have proposed several new genera and the remaining group now comprises the following: Aerococcus, Alloiococcus, Carnobacterium, Dolosigranulum, Enterococcus, Globicatella, Lactococcus, Oenococcus, Tetragenococcus, Vagococcus, and Weissella.

Their importance is associated mainly with their safe metabolic activity while growing in foods utilising available sugar for the production of organic acids and other metabolites.
Their common occurrence in foods along with their long-lived uses contributes to their natural acceptance as GRAS (Generally Recognised as Safe) for human consumption.

The three main pathways which are involved in the manufacture and development of flavour in fermented food products are as follows:
1) glycolysis (fermentation of sugars)
2) lipolysis (degradation of fat) and
3) proteolysis (degradation of proteins)

Lactate is the main product generated from the metabolism of carbohydrates and a fraction of the intermediate pyruvate can alternatively be converted to diacetyl, acetoin, acetaldehyde or acetic acid (some of which can be important for typical yogurt flavours).
The contribution of LAB to lipolysis is relatively little, but proteolysis is the key biochemical pathway for the development of flavour in fermented foods.

Degradation of such components can be further converted to various alcohols, aldehydes, acids, esters and sulphur compounds for specific flavour development in fermented food products.
The genetics of the LAB have been reviewed and complete genome sequences of a great number of LAB have been published since 2001, when the first genome of LAB was sequenced and published.

Milk acid Adjunct cultures:
Secondary cultures, or adjunct cultures or adjuncts, are defined as any cultures that are deliberately added at some point of the manufacture of fermented foods, but whose primary role is not acid production.
Adjunct cultures are used in cheese manufacture to balance some of the biodiversity removed by pasteurisation, improved hygiene and the addition of defined-strain starter culture.
These are mainly non-starter LAB which have a significant impact on flavour and accelerate the maturation process.

Extracellular polysaccharides (EPSs) are produced by a variety of bacteria and are present as capsular polysaccharides bound to the cell surface, or are released into the growth medium.
These polymers play a major role in the production of yogurt, cheese, fermented cream and milk-based desserts where they contribute to texture, mouth-feel, taste perception and stability of the final products.

In addition, Milk acid has been suggested that these EPSs or fermented milks containing these EPSs are active as prebiotics, cholesterol-lowering and immunomodulants.
EPS-producing strains of Streptococcus thermophilus and Lactobacillus delbreuckii ssp. bulgaricus have been shown to enhance the texture and viscosity of yogurt and to reduce syneresis.
For the production of wine, LAB are involved in the malolactic fermentation, that is a secondary fermentation, which involves the conversion of L-malate to L-lactate and CO2 via malate decarboxylase, also known as the malolactic enzyme, resulting in a reduction of wine acidity, providing microbiological stabilization and modifications of wine aroma.

Antifungal activities of LAB have been reported.
In addition; LAB strains also have the ability to reduce fungal mycotoxins, either by producing anti-mycotoxinogenic metabolites, or by absorbing them.
For LAB to be used as bio-protective starter cultures, they must possess a range of physical and biochemical characteristics, and most importantly, the ability to achieve growth and sufficient production of antimicrobial metabolites, which must be demonstrated in the specific food environment.

Probiotic culture:
LAB are considered as a major group of probiotic bacteria; probiotic has been defined by Fuller as "a live microbial feed supplement which beneficially affects the host animal by improving Milk acid intestinal microbial balance".
Salminen et al. proposed that probiotics are microbial cell preparations or components of microbial cells that have a beneficial effect on the health and well-being of the host.

Commercial cultures used in food applications include mainly strains of Lactobacillus spp., Bifidobacterium spp. and Propionibacterium spp. Lactobacillus acidophilus, Lactobacillus casei, Lb. reuteri, Lactobacillus rhamnosus and Lb. plantarum are the most used LAB in functional foods containing probiotics.
Argentinean Fresco cheese, Cheddar and Gouda are some examples of applications of probiotic LAB, in combination with bifidobacteria, in cheeses.

Apparently, these effects are species and strain specific, and the big challenge is the use of probiotic cultures composed of multiple species.
In addition, LAB, as part of gut microbiota ferment various substrates such as biogenic amines and allergenic compounds into short-chain fatty acids and other organic acids and gases.

In recent years, the genomes of several probiotic species have been sequenced, thus paving the way to the application of ‘omics’ technologies to the investigation of probiotic activities.
Moreover, although recombinant probiotics have been constructed, the industrial application of genetically engineered bacteria is still hampered by legal issues and by a rather negative general public opinion in the food sector.

Conclusion:
LAB are the most commonly used microorganisms for the fermentation and preservation of foods.
Their importance is associated mainly with their safe metabolic activity while growing in foods utilising available sugar for the production of organic acids and other metabolites.

Advances in the genetics, molecular biology, physiology, and biochemistry of LAB have provided new insights and applications for these bacteria.
Bacterial cultures with specific traits have been developed during the last 17 years, since the discovery of the complete genome sequence of Lc. lactis ssp. lactis IL1403 and a variety of commercial starter, functional, bio-protective and probiotic cultures with desirable properties have marketed.

However, the great challenge for food industry is to produce multiple strain cultures with multiple functions for specific products from specific regions of the world.
Also Milk acid is a challenge to produce foods, which are similar in sensory characteristics and nutritional value to the traditional products, even with special health-promoting properties, in a standardized, safe and controlled process.

Milk acid and Lactate:
Milk acid is a weak acid, which means that Milk acid only partially dissociates in water.
Milk acid dissociates in water resulting in ion lactate and H+.

This is a reversible reaction and the equilibrium is represented below.
CH3CH(OH)CO2H H+ + CH3CH(OH)CO2-Ka= 1.38 x 10-4

Depending on the environmental pH, weak acids such as Milk acid are either present as the acid in Milk acid undissociated form at low pH or as the ion salt at higher pH.
The pH at which 50% of the acid is dissociated is called the pKa, which for Milk acid is 3.86.

Under physiological circumstances the pH is generally higher than the pKa, so the majority of Milk acid in the body will be dissociated and present as lactate.
In the undissociated (unionized) form the substrates are able to pass through the lipid membranes, unlike the dissociated (ionized) form which cannot.

Milk acid (2-hydroxypropionic acid) is one of the large-scale chemical that is produced via fermentation.
The commonly used feedstocks are carbohydrates obtained from different sources like corn starch, sugarcane, or tapioca starch – depending on local availability.

The carbohydrates are hydrolyzed into monosaccharides and then fermented under the absence of oxygen by microorganisms into Milk acid.
Milk acid is the building block for polyMilk acid, but Milk acid is also used in a broad variety of food and cosmetic applications.
Bio-based Milk acid is optically active, and the production of either l-(+)- or d-(–)-Milk acid can be directed with bioengineered microorganisms.

Milk acid (2-hydroxypropionic acid) ranks among the high-volume chemicals produced microbially, with an annual world production volume in the range of 370 000 MT.
Milk acid fermentation is among the oldest industrial fermentations, with industrial production via fermentation starting in the 1880s.

Seventy-five percent of the current world Milk acid production occurs in the fermentation facilities of Galactic, PURAC Corporation, Cargill Incorporated, Archer Daniels Midland Company, and the joint ventures derived from these companies.
Historically, the primary use of Milk acid has been in food for acidulation and preservation, and Milk acid has been granted GRAS (generally recognized as safe) status by the FDA.
Milk acid also finds uses in leather tanning, cosmetics, pharmaceutical applications, as well as various other niches.

World Milk acid production has expanded 10-fold in the last decade due, in large part, to increased demand for green products derived from Milk acid, including ethyl lactate and polyMilk acid (PLA).
Ethyl lactate can be utilized in a variety of green solvents, and although Milk acid low human toxicity relative to hydrocarbon alternatives is attractive, price is cited as the primary reason for Milk acid limited market use.

PLA is a polymer that is considered a green alternative to petroleum-derived plastics due to Milk acid biodegradability and reduced carbon footprint.
PLA products are on the market in a wide range of applications including packaging, fibers, and foams.
The world’s major producer of PLA is NatureWorks LLC, currently wholly owned by Cargill Incorporated.

The primary cost in the production of PLA and ethyl lactate is the cost of raw material, that is, Milk acid.
The key parameters that determine the cost of Milk acid are rate, titer, and yield, in both fermentation and downstream product recovery unit operations.

Furthermore, Milk acid production accounts for a large fraction of the energy input and greenhouse gas (GHG) emissions in Milk acid-derived products.
These carbon costs can be of great concern in the marketing and viability of a green product.

As discussed previously, Milk acid production has occurred for over 100 years, with only modest changes to conditions or host organisms.
Milk acid is produced via fermentation, traditionally carried out by bacteria belonging to the genera Lactobacillus, Lactococcus, Streptococcus, Bacillus, and Enterococcus.

For the recent applications of Milk acid as a green chemical intermediate, for example, for PLA, the cost of production via traditional process is too high.
As a result, a production strain for industrial Milk acid must fit the following criteria: production of > 100 g l−1 Milk acid at yields near theoretical (0.9 g Milk acid per gram of dextrose), high chiral purity of Milk acid produced (> 99%) with rates, media, and recovery costs able to meet the above cost targets.
Lowering this production cost holds the potential to expand the market for both Milk acid and Milk acid green derivatives.

The primary costs associated with fermentation are the nutrients and sugars required for cell growth and Milk acid production along with the downstream recovery and purification process.
In addition to a sugar source, traditional bacterial lactic fermentations typically require an organic nitrogen source (such as yeast extract or corn steep liquor) along with B vitamin supplementation.

Furthermore, these fermentations require that the pH be maintained in the range of 5–7, well above the pKa of Milk acid.
Maintaining the pH in this range requires neutralization of the Milk acid during fermentation, followed by costly downstream steps or acidulation to regenerate free Milk acid.
This greatly increases the cost of fermentation.

In 2008, Cargill implemented a new-to-the-world fermentation technology involving genetically modified yeast capable of producing Milk acid at industrially relevant rates, titers, and yields at pH values ≤ 3.0, which is well below the pKa of Milk acid.
The low-pH fermentation process results in improved product quality and downstream processing, reduced chemical usage and nutrient costs, and a 35% reduction in the GHG emissions associated with Milk acid production by fermentation.

Additionally, the potential for product loss due to bacteriophage attacks and microbial contamination that can occur in the traditional bacterial process are eliminated or greatly reduced with the low-pH yeast process.
This increased process robustness contributes to reduction in the overall cost of Milk acid production and subsequently has helped to grow the market for Milk acid and Milk acid derivatives.

Future advances in the low-pH yeast process are expected to lower the cost of Milk acid production even more by reducing the cost of the carbon source fermented to Milk acid.
To achieve this, low-pH yeasts need to be further developed to efficiently ferment low-cost carbon sources to free Milk acid.
Milk acid was estimated by life cycle analysis that through the use of cellulosic feedstocks derived from biomass and the use of wind power to produce Milk acid and PLA, the overall GHG emissions could be calculated as a net negative

Applications of Milk acid:

Pharmaceutical and cosmetic applications:
Milk acid is also employed in pharmaceutical technology to produce water-soluble lactates from otherwise-insoluble active ingredients.
Milk acid finds further use in topical preparations and cosmetics to adjust acidity and for Milk acid disinfectant and keratolytic properties.

Foods:
Milk acid is found primarily in sour milk products, such as koumiss, laban, yogurt, kefir, and some cottage cheeses.
The casein in fermented milk is coagulated (curdled) by Milk acid.
Milk acid is also responsible for the sour flavor of sourdough bread.

In lists of nutritional information Milk acid might be included under the term "carbohydrate" (or "carbohydrate by difference") because this often includes everything other than water, protein, fat, ash, and ethanol.
If this is the case then the calculated food energy may use the standard 4 kilocalories (17 kJ) per gram that is often used for all carbohydrates.

But in some cases Milk acid is ignored in the calculation.
The energy density of Milk acid is 362 kilocalories (1,510 kJ) per 100 g.

Some beers (sour beer) purposely contain Milk acid, one such type being Belgian lambics.
Most commonly, this is produced naturally by various strains of bacteria.

These bacteria ferment sugars into acids, unlike the yeast that ferment sugar into ethanol.
After cooling the wort, yeast and bacteria are allowed to “fall” into the open fermenters.

Brewers of more common beer styles would ensure that no such bacteria are allowed to enter the fermenter.
Other sour styles of beer include Berliner weisse, Flanders red and American wild ale.

In winemaking, a bacterial process, natural or controlled, is often used to convert the naturally present malic acid to Milk acid, to reduce the sharpness and for other flavor-related reasons.
This malolactic fermentation is undertaken by Milk acid bacteria.
While not normally found in significant quantities in fruit, Milk acid is the primary organic acid in akebia fruit, making up 2.12% of the juice.

As a food additive Milk acid is approved for use in the EU, USA and Australia and New Zealand; Milk acid is listed by Milk acid INS number 270 or as E number E270.
Milk acid is used as a food preservative, curing agent, and flavoring agent.

Forgery:
Milk acid has historically been used to assist with the erasure of inks from official papers to be modified during forgery.

Cleaning products:
Milk acid is used in some liquid cleaners as a descaling agent for removing hard water deposits such as calcium carbonate, forming the lactate, Calcium lactate.
Owing to Milk acids high acidity, such deposits are eliminated very quickly, especially where boiling water is used, as in kettles.
Milk acid also is gaining popularity in antibacterial dish detergents and hand soaps replacing Triclosan.

Uses of Milk acid:
Milk acid is used as a solvent and acidulant in the production of foods, drugs, and dyes.
Milk acid is also used as a mordant in woolen goods printing, a soldering flux, a dehairing agent, and a catalyst for phenolic resins.
Milk acid is also used in leather tanning, oil well acidizing, and as a plant growth regulator.

The fastest growing use for Milk acid is Milk acid use as a monomer for the production of polyMilk acid or polylactide (PLA).
Applications for PLA include containers for the food and beverage industries, films and rigid containers for packaging, and serviceware (cups, plates, utensils).
The PLA polymer can also be spun into fibers and used in apparel, fiberfill (pillows, comforters), carpet, and nonwoven applications such as wipes.

Milk acid is used in metal plating, cosmetics, and the textile and leather industry.

Milk acid is used in dyeing baths, as mordant in printing woolen goods, solvent for water-insoluble dyes (alcohol-soluble induline, nigrosine, spirit-blue).
Milk acid is used in reducing chromates in mordanting wool.

Milk acid is used in manufacturing cheese, confectionery.
Milk acid is used in component of babies' milk formulas; acidulant in beverages; for acidulating worts in brewing.

Milk acid is used in in preparation of sodium lactate injections.
Milk acid is used in ingredient of cosmetics.

Milk acid is used in component of spermatocidal jellies.
Milk acid is used in for removing Clostridium butyricum in manufacturing of yeast; dehairing, plumping, and decalcifying hides.

Milk acid is used in solvent for cellulose formate.
Milk acid is used in flux for soft solder.

Milk acid is used in manufacturing lactates which are used in food products, in medicine, and as solvents.
Milk acid is used in plasticizer, catalyst in the casting of phenolaldehyde resins.

Milk acid in Food:
Milk acid is naturally present in many foodstuffs.
Milk acid is formed by natural fermentation in products such as cheese, yogurt, soy sauce, sourdough, meat products and pickled vegetables.

Milk acid is also used in a wide range of food applications such as bakery products, beverages, meat products, confectionery, dairy products, salads, dressings, ready meals, etc.
Milk acid in food products usually serves as either as a pH regulator or as a preservative.
Milk acid is also used as a flavoring agent.

Meat, Poultry & Fish:
Milk acid can be used in meat, poultry and fish in the form of sodium or potassium lactate to extend shelf life, control pathogenic bacteria (improve food safety), enhance and protect meat flavor, improve water binding capacity and reduce sodium.

Beverages:
Because of Milk acid mild taste, Milk acid is used as an acidity regulator in beverages such as soft drinks and fruit juices.

Pickled vegetables:
Milk acid is effective in preventing the spoilage of olives, gherkins, pearl onions and other vegetables preserved in brine.

Salads & dressings:
Milk acid may be also used as a preservative in salads and dressings, resulting in products with a milder flavor while maintaining microbial stability and safety.

Confectionery:
Formulating hard-boiled candy, fruit gums and other confectionery products with Milk acid results in a mild acid taste, improved quality, reduced stickiness and longer shelf life.

Dairy:
The natural presence of Milk acid in dairy products, combined with the dairy flavor and good antimicrobial action of Milk acid, makes Milk acid an excellent acidification agent for many dairy products.

Baked Goods:
Milk acid is a natural sourdough acid, which gives the bread Milk acid characteristic flavor, and therefore Milk acid can be used for direct acidification in the production of sourdough.

Savory Flavors:
Milk acid is used to enhance a broad range of savory flavors.
Milk acids natural occurrence in meat and dairy products makes Milk acid an attractive way to enhance savory flavors.

Pharmaceutical:
The primary functions for the pharmaceutical applications are: pH-regulation, metal sequestration, chiral intermediate and as a natural body constituent in pharmaceutical products.

Biomaterials:
Milk acid is a valuable component in biomaterials such as resorbable screws, sutures and medical devices.

Detergents:
Milk acid well known for Milk acid descaling properties and is widely applied in household cleaning products.
Also, Milk acid is used as a natural anti-bacterial agent in disinfecting products.

Technical:
Milk acid is used in a wide variety of industrial processes where acidity is required and where Milk acid properties offer specific benefits.
Examples are the manufacture of leather and textile products and computer disks, as well as car coating.

Animal Feed:
Milk acid is a commonly used additive in animal nutrition.
Milk acid has health promoting properties, thus enhancing the performance of farm animals.

Milk acid can be used as an additive in food and/or drinking water.
Milk acid in biodegradable plastics

Milk acid is the principal building block for Poly Milk acid (PLA).
PLA is a biobased and bio-degradable polymer that can be used for producing renewable and compostable plastics.

Industry Uses:
Agricultural chemicals (non-pesticidal)
Intermediate
Not Known or Reasonably Ascertainable
Plating agents and surface treating agents
Process regulators
Processing aids, not otherwise listed

Consumer Uses:
Agricultural chemicals (non-pesticidal)
Intermediate
Preservative
Processing aids, not otherwise listed

Industrial Processes with risk of exposure:
Petroleum Production and Refining
Soldering
Farming (Pesticides)
Leather Tanning and Processing
Fur Dressing and Dyeing
Textiles (Printing, Dyeing, or Finishing)

Milk acid, is an organic acid with applications in beer production as well as the cosmetic, pharmaceutical, food and chemical industries.

KEYWORDS:
50-21-5, 200-018-0, lactic acid, 2-hydroxypropanoic acid, DL-Lactic acid, Tonsillosan, Ethylidenelactic acid, Acidum lacticum, DL-Milchsaeure, Lactic acid USP

Biology of Milk acid:
l-Milk acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA1), a Gi/o-coupled G protein-coupled receptor (GPCR).

Exercise and lactate:
During power exercises such as sprinting, when the rate of demand for energy is high, glucose is broken down and oxidized to pyruvate, and lactate is then produced from the pyruvate faster than the body can process it, causing lactate concentrations to rise.
The production of lactate is beneficial for NAD+ regeneration (pyruvate is reduced to lactate while NADH is oxidized to NAD+), which is used up in oxidation of glyceraldehyde 3-phosphate during production of pyruvate from glucose, and this ensures that energy production is maintained and exercise can continue.
During intense exercise, the respiratory chain cannot keep up with the amount of hydrogen ions that join to form NADH, and cannot regenerate NAD+ quickly enough.

The resulting lactate can be used in two ways:
Oxidation back to pyruvate by well-oxygenated muscle cells, heart cells, and brain cells
Pyruvate is then directly used to fuel the Krebs cycle

Conversion to glucose via gluconeogenesis in the liver and release back into circulation; see Cori cycle
If blood glucose concentrations are high, the glucose can be used to build up the liver's glycogen stores.

However, lactate is continually formed even at rest and during moderate exercise.
Some causes of this are metabolism in red blood cells that lack mitochondria, and limitations resulting from the enzyme activity that occurs in muscle fibers having high glycolytic capacity.

In 2004, Robergs et al. maintained that Milk acidosis during exercise is a "construct" or myth, pointing out that part of the H+ comes from ATP hydrolysis (ATP4− + H2O → ADP3− + HPO2− 4 + H+), and that reducing pyruvate to lactate (pyruvate− + NADH + H+ → lactate− + NAD+) actually consumes H+.
Lindinger et al. countered that they had ignored the causative factors of the increase in [H+].

After all, the production of lactate− from a neutral molecule must increase [H+] to maintain electroneutrality.
The point of Robergs's paper, however, was that lactate− is produced from pyruvate−, which has the same charge.

Milk acid is pyruvate− production from neutral glucose that generates H+:
C6H12O6 + 2 NAD+ + 2 ADP3− + 2 HPO2−4 → 2 CH3COCO−2 + 2 H+ + 2 NADH + 2 ATP4− + 2 H2O

Subsequent lactate− production absorbs these protons:
2 CH3COCO−2 + 2 H+ + 2 NADH → 2 CH3CH(OH)CO−2 + 2 NAD+

Overall:
C6H12O6 + 2 NAD+ + 2 ADP3− + 2 HPO2−4 → 2 CH3COCO−2 + 2 H+ + 2 NADH + 2 ATP4− + 2 H2O→ 2 CH3CH(OH)CO−2 + 2 NAD+ + 2 ATP4− + 2 H2O
Although the reaction glucose → 2 lactate− + 2 H+ releases two H+ when viewed on Milk acid own, the H+ are absorbed in the production of ATP.

On the other hand, the absorbed acidity is released during subsequent hydrolysis of ATP: ATP4− + H2O → ADP3− + HPO2−4 + H+.
So once the use of ATP is included, the overall reaction is C6H12O6 → 2 CH3COCO−2 + 2 H+.
The generation of CO2 during respiration also causes an increase in [H+].

Metabolism of Milk acid:
Although glucose is usually assumed to be the main energy source for living tissues, there are some indications that Milk acid is lactate, and not glucose, that is preferentially metabolized by neurons in the brain of several mammalian species (the notable ones being mice, rats, and humans).
According to the lactate-shuttle hypothesis, glial cells are responsible for transforming glucose into lactate, and for providing lactate to the neurons.
Because of this local metabolic activity of glial cells, the extracellular fluid immediately surrounding neurons strongly differs in composition from the blood or cerebrospinal fluid, being much richer with lactate, as was found in microdialysis studies.

Some evidence suggests that lactate is important at early stages of development for brain metabolism in prenatal and early postnatal subjects, with lactate at these stages having higher concentrations in body liquids, and being utilized by the brain preferentially over glucose.
Milk acid was also hypothesized that lactate may exert a strong action over GABAergic networks in the developing brain, making them more inhibitory than Milk acid was previously assumed,acting either through better support of metabolites, or alterations in base intracellular pH levels, or both.

Studies of brain slices of mice show that β-hydroxybutyrate, lactate, and pyruvate act as oxidative energy substrates, causing an increase in the NAD(P)H oxidation phase, that glucose was insufficient as an energy carrier during intense synaptic activity and, finally, that lactate can be an efficient energy substrate capable of sustaining and enhancing brain aerobic energy metabolism in vitro.
The study "provides novel data on biphasic NAD(P)H fluorescence transients, an important physiological response to neural activation that has been reproduced in many studies and that is believed to originate predominately from activity-induced concentration changes to the cellular NADH pools."

Lactate can also serve as an important source of energy for other organs, including the heart and liver.
During physical activity, up to 60% of the heart muscle's energy turnover rate derives from lactate oxidation.

Blood testing:
Blood tests for lactate are performed to determine the status of the acid base homeostasis in the body.
Blood sampling for this purpose is often arterial (even if Milk acid is more difficult than venipuncture), because lactate levels differ substantially between arterial and venous, and the arterial level is more representative for this purpose.

Polymer precursor:
Two molecules of Milk acid can be dehydrated to the lactone lactide.
In the presence of catalysts lactide polymerize to either atactic or syndiotactic polylactide (PLA), which are biodegradable polyesters.
PLA is an example of a plastic that is not derived from petrochemicals.

Production of Milk acid:
Milk acid is produced industrially by bacterial fermentation of carbohydrates, or by chemical synthesis from acetaldehyde.
In 2009, Milk acid was produced predominantly (70–90%) by fermentation.

Production of racemic Milk acid consisting of a 1:1 mixture of d and l stereoisomers, or of mixtures with up to 99.9% l-Milk acid, is possible by microbial fermentation.
Industrial scale production of d-Milk acid by fermentation is possible, but much more challenging.

As a starting material for industrial production of Milk acid, almost any carbohydrate source containing C5 and C6 sugars can be used.
Pure sucrose, glucose from starch, raw sugar, and beet juice are frequently used.
Milk acid producing bacteria can be divided in two classes: homofermentative bacteria like Lactobacillus casei and Lactococcus lactis, producing two moles of lactate from one mole of glucose, and heterofermentative species producing one mole of lactate from one mole of glucose as well as carbon dioxide and acetic acid/ethanol.

Milk acid was the first organic acid produced with microbes, carried out in 1880.
In the twenty-first century, synthetic processes for the production of Milk acid (e.g., from lactonitrile) are competitive at the same costs as biological processes; Milk acid production is divided about equally between the two processes.
The major supply of Milk acid in Europe is produced by fermentation using strains of L. bulgaricus when whey is used as the substrate, and other lactobacilli when different substrates are used.

According to the U.S. Food and Drug Administrating (FDA), Milk acid is a generally recognized as safe (GRAS) additive for miscellaneous or general purpose uses.
Milk acid was one of the earliest organic acids used in foods.

Milk acid is used by the food industry in a number of ways:
Milk acid is used in packing Spanish olives, where Milk acid inhibits spoilage and further fermentation.

Milk acid aids in the stabilization of dried-egg powder.
Milk acid improves the taste of certain pickles when added to vinegar.

Milk acid is used to acidify the grape juice (must) in winemaking.
In frozen confections, Milk acid imparts a milky tart taste and does not mask other natural flavors.

Milk acid is also used in the production of the emulsifiers calcium and sodium stearoyl lactylates, which function as dough conditioners.
The sodium and potassium salts of Milk acid have significant antimicrobial properties, including in meat products against toxin production by Clostridium botulinum, and against Listeria monocytogenes in chicken, beef, and smoked salmon

Milk acid is present in many foods both naturally and as a product of in situ fermentation, as in sauerkraut, yogurt, and many other fermented foods.
Milk acid is also a principal metabolic intermediate in most living organisms.

Sodium and potassium lactates are produced commercially by neutralization of natural or synthetic Milk acid (FDA 184.1768, 1639).
Milk acid to be used as a food additive can be obtained either by fermentation of carbohydrates or by a chemical procedure involving formation of lactonitrile from acetaldehyde and hydrogen cyanide and subsequent hydrolysis (FDA 184.1061).

The microbiological and chemical procedures to obtain Milk acid are very competitive, with similar production costs.
One method of biosynthesis in common use starts with glucose and produces pyruvate, which can be converted to both the l(+) and d(−) isomers using a stereospecific lactate dehydrogenase; however, only the l(+) form is produced commercially.

The racemic mixture is always obtained by chemical synthesis.
Synthetic Milk acid is free of the contaminants normally found in the product obtained by fermentation, and so Milk acid is completely colorless and probably more stable.

Milk acid and its salts are highly hygroscopic, and therefore are usually handled in concentrated solutions (60–80% by weight) rather than in solid form.
These solutions are colorless and odorless, and have a mild saline taste

Chemical production:
Racemic Milk acid is synthesized industrially by reacting acetaldehyde with hydrogen cyanide and hydrolysing the resultant lactonitrile.
When hydrolysis is performed by hydrochloric acid, ammonium chloride forms as a by-product; the Japanese company Musashino is one of the last big manufacturers of Milk acid by this route.
Synthesis of both racemic and enantiopure Milk acids is also possible from other starting materials (vinyl acetate, glycerol, etc.) by application of catalytic procedures.

General Manufacturing Information of Milk acid:

Industry Processing Sectors:
Agriculture, Forestry, Fishing and Hunting
All Other Basic Organic Chemical Manufacturing
All Other Chemical Product and Preparation Manufacturing
Food, beverage, and tobacco product manufacturing
Oil and Gas Drilling, Extraction, and Support activities
Paint and Coating Manufacturing
Pesticide, Fertilizer, and Other Agricultural Chemical Manufacturing
Plastics Material and Resin Manufacturing
Plastics Product Manufacturing

History of Milk acid:
Swedish chemist Carl Wilhelm Scheele was the first person to isolate Milk acid in 1780 from sour milk.
The name reflects the lact- combining form derived from the Latin word lac, which means milk.

In 1808, Jöns Jacob Berzelius discovered that Milk acid (actually l-lactate) also is produced in muscles during exertion.
Milk acids structure was established by Johannes Wislicenus in 1873.

In 1856, the role of Lactobacillus in the synthesis of Milk acid was discovered by Louis Pasteur.
This pathway was used commercially by the German pharmacy Boehringer Ingelheim in 1895.
In 2006, global production of Milk acid reached 275,000 tonnes with an average annual growth of 10%.

Identifiers of Milk acid:
CAS Number:
50-21-5
79-33-4 (l)
10326-41-7 (d)

3DMet: B01180
Beilstein Reference: 1720251
ChEBI: CHEBI:422
ChEMBL: ChEMBL330546
ChemSpider: 96860
ECHA InfoCard: 100.000.017
EC Number: 200-018-0
E number: E270 (preservatives)
Gmelin Reference: 362717
IUPHAR/BPS: 2932
KEGG: C00186
PubChem CID: 612
RTECS number: OD2800000

UNII:
3B8D35Y7S4
F9S9FFU82N (l)
3Q6M5SET7W (d)

UN number: 3265
CompTox Dashboard (EPA): DTXSID7023192
InChI: InChI=1S/C3H6O3/c1-2(4)3(5)6/h2,4H,1H3,(H,5,6)/t2-/m0/s1
Key: JVTAAEKCZFNVCJ-REOHCLBHSA-N
SMILES: CC(O)C(=O)O

Properties of Milk acid:
Chemical formula: C3H6O3
Molar mass: 90.078 g·mol−1
Melting point: 18 °C (64 °F; 291 K)
Boiling point: 122 °C (252 °F; 395 K) at 15 mmHg
Solubility in water: Miscible
Acidity (pKa): 3.86, 15.1

Boiling point: 122 °C (20 hPa)
Density: 1.21 g/cm3 (20 °C)
Melting Point: 18 °C
pH value: 2.8 (10 g/l, H₂O, 20 °C)
Vapor pressure: 0.1 hPa (25 °C)

Molecular Weight: 90.08 g/mol
XLogP3: -0.7
Hydrogen Bond Donor Count: 2
Hydrogen Bond Acceptor Count: 3
Rotatable Bond Count: 1
Exact Mass: 90.031694049 g/mol
Monoisotopic Mass: 90.031694049 g/mol
Topological Polar Surface Area: 57.5Å²
Heavy Atom Count: 6
Complexity: 59.1
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 1
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes

Specifications of Milk acid:
Assay (alkalimetric): 88.0 - 92.0 %
Assay (stereochemical purity of (S)-lactic acid): ≥ 95.0 %
Identity (IR-spectrum): passes test
Identity (pH): passes test
Identity (Density): passes test
Identity (Lactat): passes test
Identity (assay): passes test
Appearance: clear, oily liquid, not more intense in color than reference solution Y₆
Ether-insoluble substances: passes test
Citric, oxalic and Phosphoric acids: passes test
Density (d 20/20): 1.20 - 1.21
Chloride (Cl): ≤ 0.2 %
Sulfate (SO₄): ≤ 200 ppm
As (Arsenic): ≤ 3 ppm
Ca (Calcium): ≤ 200 ppm
Fe (Iron): ≤ 10 ppm
Hg (Mercury): ≤ 1 ppm
Pb (Lead): ≤ 2 ppm
Ethanol: ≤ 5000 ppm
Acetic acid: ≤ 5000 ppm
Methanol: ≤ 50 ppm
Other residual solvents (ICH Q3C): excluded by manufacturing process
Sugars and other reducing substances: passes test
Sulfated ash (600 °C): ≤ 0.10 %
Total aerobic microbial count (TAMC): ≤ 10²
Total combined yeasts/moulds count (TYMC): ≤ 10²
Bacterial endotoxins: ≤ 5 I.U./g

Thermochemistry of Milk acid:
Std enthalpy of combustion (ΔcH⦵298): 1361.9 kJ/mol, 325.5 kcal/mol, 15.1 kJ/g, 3.61 kcal/g

Pharmacology of Milk acid:
ATC code: G01AD01 (WHO) QP53AG02 (WHO)

Related compounds of Milk acid:
1-Propanol
2-Propanol
Propionaldehyde
Acrolein
Sodium lactate
Ethyl lactate

Other anions:
Lactate
Related carboxylic acids:
Acetic acid
Glycolic acid
Propionic acid
3-Hydroxypropanoic acid
Malonic acid
Butyric acid
Hydroxybutyric acid

Some examples of lactates (salts or esters of lactic acid) are:
Ammonium Lactate (NH4C3H5O3, CAS RN: 515-98-0): clear to yellow, syrupy liquid used in in electroplating, in finishing leather and as humectant for food, pharmaceutical, and cosmetics.
Butyl Lactate (CH3CHOHCOOC4H9, CAS RN:138-22-7): a clear liquid: nontoxic, miscible with many solvents; used as a solvent for varnish, lacquers, resins and gums, used in making paints, inks, dry cleaning fluid, flavoring and as a chemical intermediate.
Calcium Lactate Pentahydrate [Ca(C3H5O3)2·5H2O, CAS RN: 814-80-2] : white crystals; soluble in water; used as a calcium source; administered orally in the treatment of calcium deficiency; as a blood coagulant.
Ethyl Lactate (CH3CHOHCOOC2H5, CAS RN: 97-64-3): clear liquid with mild odur; boiling point 154 C; miscible with alcohols, ketones, esters, and hydrocarbons as well as with water; used in pharmaceutical preparations, feed additive, as a flavoring ( odor description: sweet butter, coconut, fruity, creamy dairy, butterscotch) and as a solvent for cellulose compounds such as nitrocellulose, cellulose acetate, and cellulose ethers.
Magnesium Lactate Trihydrate [Mg(C3H5O3)2·3H2O, CAS RN: 18917-93-6 ]: white crystals with bitter taste; soluble in water, slightly soluble in alcohol; used in medicine and as an electrolyte replenisher.
Manganese Lactate Trihydrate [Mn(C3H5O3)2·3H2O]: pale red crystals; insoluble in water and alcohol; used in medicine.
Mercuric Lactate [Hg(C3H5O3)2]: poisonous white powder that decomposes when heated; soluble in water; used in medicine.
Methyl Lactate (CH3CHCHCOOCH3): clear liquid with mild odur; boiling point 145 C; miscible with alcohols, ketones, esters, and hydrocarbons as well as with water; used in pharmaceutical preparations, feed additive, as a flavoring and as a solvent for cellulose compounds such as nitrocellulose, cellulose acetate, and cellulose ethers.
Sodium Lactate (CH3CHOHCOONa, CAS RN: 72-17-3) clear to yellow, hygroscopic syrupy liquid; soluble in water; melting point 17 C; used in medicine, in antifreeze, and hygroscopic agent and as a corrosion inhibitor.
Zinc Lactate (Zn(C3H5O3)2·2H2O, CAS RN: 16039-53-5): white crystals; used as an additive in toothpaste and food; preparation of drugs.

Names of Milk acid:

Preferred IUPAC name:
2-Hydroxypropanoic acid

Other names:
Lactic acid
Milk acid

Synonyms of Milk acid:
lactic acid
2-hydroxypropanoic acid
DL-Lactic acid
50-21-5
2-hydroxypropionic acid
Milk acid
lactate
Tonsillosan
Racemic lactic acid
Ordinary lactic acid
Ethylidenelactic acid
Lactovagan
Acidum lacticum
26100-51-6
Milchsaeure
Lactic acid, dl-
Kyselina mlecna
Lacticum acidum
DL-Milchsaeure
Lactic acid USP
(+/-)-Lactic acid
Propanoic acid, 2-hydroxy-
Aethylidenmilchsaeure
598-82-3
1-Hydroxyethanecarboxylic acid
alpha-Hydroxypropionic acid
Lactic acid (natural)
(RS)-2-Hydroxypropionsaeure
FEMA No. 2611
Milchsaure
Kyselina 2-hydroxypropanova
Lurex
Propionic acid, 2-hydroxy-
Purac FCC 80
Purac FCC 88
Cheongin samrakhan
FEMA Number 2611
CCRIS 2951
HSDB 800
Cheongin Haewoohwan
Cheongin Haejanghwan
SY-83
2-Hydroxypropionicacid
(+-)-2-Hydroxypropanoic acid
Biolac
NSC 367919
Lactic acid, tech grade
Propanoic acid, hydroxy-
Chem-Cast
alpha-Hydroxypropanoic acid
AI3-03130
HIPURE 88
DL- lactic acid
EINECS 200-018-0
EINECS 209-954-4
EPA Pesticide Chemical Code 128929
Lactic acid,buffered
NSC-367919
UNII-3B8D35Y7S4
2-Hydroxy-2-methylacetic acid
BRN 5238667
INS NO.270
DTXSID7023192
(+/-)-2-hydroxypropanoic acid
CHEBI:78320
INS-270
3B8D35Y7S4
E 270
MFCD00004520
LACTIC ACID (+-)
.alpha.-Hydroxypropanoic acid
.alpha.-Hydroxypropionic acid
DTXCID003192
E-270
EC 200-018-0
NCGC00090972-01
2-hydroxy-propionic acid
(R)-2-Hydroxy-propionic acid;H-D-Lac-OH
C01432
Milchsaure [German]
Lactic acid [JAN]
Kyselina mlecna [Czech]
D(-)-lactic acid
CAS-50-21-5
2 Hydroxypropanoic Acid
2 Hydroxypropionic Acid
Kyselina 2-hydroxypropanova [Czech]
Lactic acid [USP:JAN]
lactasol
1-Hydroxyethane 1-carboxylic acid
acido lactico
DL-Milchsaure
(2RS)-2-Hydroxypropanoic acid
L- Lactic acid
Lactate (TN)
4b5w
Propanoic acid, (+-)
DL-Lactic Acid, Racemic
LACTIC ACID (II)
(.+/-.)-Lactic acid
Lactic acid (7CI,8CI)
Lactic acid (JP17/USP)
Lactic acid, 85%, FCC
Lactic Acid, Racemic, USP
NCIOpen2_000884
(+-)-LACTIC ACID
DL-LACTIC ACID [MI]
LACTIC ACID [WHO-IP]
(RS)-2-hydroxypropanoic acid
LACTIC ACID, DL-(II)
LACTICUM ACIDUM [HPUS]
1-hydroxyethane carboxylic acid
33X04XA5AT
DL-Lactic Acid (90per cent)
CHEMBL1200559
Lactic acid, natural, >=85%
BDBM23233
L-lactic acid or dl-lactic acid
Lactic Acid, 85 Percent, FCC
LACTIC ACID, DL- [II]
DL-Lactic acid, ~90% (T)
DL-Lactic acid, AR, >=88%
DL-Lactic acid, LR, >=88%
DL- LACTIC ACID [WHO-DD]
LACTIC ACID (EP MONOGRAPH)
Lactic Acid, 10 Percent Solution
HY-B2227
LACTIC ACID (USP MONOGRAPH)
Propanoic acid, 2-hydroxy- (9CI)
Tox21_111049
Tox21_202455
Tox21_303616
BBL027466
NSC367919
STL282744
AKOS000118855
AKOS017278364
Tox21_111049_1
ACIDUM LACTICUM [WHO-IP LATIN]
AM87208
DB04398
SB44647
SB44652
Propanoic acid,2-hydroxy-,(.+/-.)-
2-Hydroxypropionic acid, DL-Lactic acid
NCGC00090972-02
NCGC00090972-03
NCGC00257515-01
NCGC00260004-01
26811-96-1
Lactic Acid, 85 Percent, Reagent, ACS
CS-0021601
FT-0624390
FT-0625477
FT-0627927
FT-0696525
FT-0774042
L0226
EN300-19542
Lactic acid, meets USP testing specifications
D00111
F71201
A877374
DL-Lactic acid, SAJ first grade, 85.0-92.0%
Q161249
DL-Lactic acid, JIS special grade, 85.0-92.0%
F2191-0200
Z104474158
BC10F553-5D5D-4388-BB74-378ED4E24908
Lactic acid, United States Pharmacopeia (USP) Reference Standard
Lactic acid, Pharmaceutical Secondary Standard; Certified Reference Material
DL-Lactic acid 90%, synthetic, meets the analytical specifications of Ph. Eur.
152-36-3