Молочная кислота

Химические свойства

Lactic acid, CH3CHOHCOOH, also known as 2-hydroxypropanoic acid, is a hygroscopic liquid that exists in three isometric forms. I-lactic acid is found in blood and animal tissue as a product of glucose and glycogen metabolism. d-Iactic acid is obtained by fermentation of sucrose (corn refining), The racemic mixture is present in foods prepared by bacterial fermentation or prepared synthetically. Lactic acid is soluble in water,alcohol,and ether. It is used as a solvent, in manufacturing confectionery, and in medicine.

Вхождение

Reported found in Papaver somniferum L.; it is a constituent of wine and sour milk; the two optically active isomers are found in muscular tissues and are formed by the action of lactic acid–producing bacteria in several fermentation processes. Also reported found in guava, grapes, melon, wheat bread, cheeses, yogurt, milk, cream, buttermilk, egg, cooked beef, cognac, cider, sherry, grape wine, beer, grape brandy, whiskey, cocoa, coffee, tea, mango, sake, wort, dried, bonito, cassava, Bourbon vanilla, chicory root, Cape gooseberry and cherimoya.

Использование

lactic acid (sodium lactate) is a multi-purpose ingredient used as a preservative, exfoliant, moisturizer, and to provide acidity to a formulation. In the body, lactic acid is found in the blood and muscle tissue as a product of the metabolism of glucose and glycogen. It is also a component of the skin’s natural moisturizing factor. Lactic acid has better water intake than glycerin. Studies indicate an ability to increase the water-retention capacity of the stratum corneum. They also show that the pliability of the stratum corneum layer is closely related to the absorption of lactic acid; that is, the greater the amount of absorbed lactic acid, the more pliable the stratum corneum layer. Researchers report that continuous use of preparations formulated with lactic acid in concentrations ranging between 5 and 12 percent provided a mild to moderate improvement in fine wrinkling and promote softer, smoother skin. Its exfoliating properties can help in the process of removing excess pigment from the surface of the skin, as well as improving skin texture and feel. Lactic acid is an alpha hydroxy acid occurring in sour milk and other lesser-known sources, such as beer, pickles, and foods made through a process of bacterial fermentation. It is caustic when applied to the skin in highly concentrated solutions.

Определение

ChEBI: A 2-hydroxy monocarboxylic acid that is propanoic acid in which one of the alpha-hydrogens is replaced by a hydroxy group.

Методы производства

Lactic acid is prepared by the fermentation of carbohydrates, such as glucose, sucrose, and lactose, with Bacillus acidi lacti or related microorganisms. On a commercial scale, whey, corn starch, potatoes, or molasses are used as a source of carbohydrate. Lactic acid may also be prepared synthetically by the reaction between acetaldehyde and carbon monoxide at 130–200°C under high pressure, or by the hydrolysis of hexoses with sodium hydroxide.
Lactic acid prepared by the fermentation of sugars is levorotatory; lactic acid prepared synthetically is racemic. However, lactic acid prepared by fermentation becomes dextrorotatory on dilution with water owing to the hydrolysis of (R)-lactic acid lactate to (S)- lactic acid.

Общее описание

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.

Реакции воздуха и воды

Soluble in water.

Угроза здоровью

Inhalation of mist causes coughing and irritation of mucous membranes. Ingestion, even of diluted preparations, has a corrosive effect on the esophagus and stomach. Contact with more concentrated solutions can cause severe burns of skin or eye.

Пожароопасность

Combustible material: may burn but does not ignite readily. When heated, vapors may form explosive mixtures with air: indoors, outdoors and sewers explosion hazards. Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated. Runoff may pollute waterways. Substance may be transported in a molten form.

Фармацевтические приложения

Lactic acid is used in beverages, foods, cosmetics, and pharmaceuticals as an acidifying agent and acidulant.
In topical formulations, particularly cosmetics, it is used for its softening and conditioning effect on the skin. Lactic acid may also be used in the production of biodegradable polymers and microspheres, such as poly(D-lactic acid), used in drug delivery systems.
Lactic acid is also used as a food preservative. Therapeutically, lactic acid is used in injections, in the form of lactate, as a source of bicarbonate for the treatment of metabolic acidosis; as a spermicidal agent; in pessaries for the treatment of leukorrhea; in infant feeds; and in topical formulations for the treatment of warts.

Промышленное использование

lactic acid showed good depressing effect on hornblende, pyroxene and biotite during flotation of hematite and ilmenite minerals.

Безопасность

Lactic acid occurs in appreciable quantities in the body as an end product of the anaerobic metabolism of carbohydrates and, while harmful in the concentrated form , can be considered nontoxic at the levels at which it is used as an excipient. A 1% v/v solution, for example, is harmless when applied to the skin.
There is evidence that neonates have difficulty in metabolizing (R)-lactic acid, and this isomer and the racemate should therefore not be used in foods intended for infants aged less than 3 months old.
There is no evidence that lactic acid is carcinogenic, teratogenic, or mutagenic.
LD50 (guinea pig, oral): 1.81 g/kg
LD50 (mouse, oral): 4.88 g/kg
LD50 (mouse, SC): 4.5 g/kg
LD50 (rat, oral): 3.73 g/kg

хранилище

Lactic acid is hygroscopic and will form condensation products such as polylactic acids on contact with water. The equilibrium between the polylactic acids and lactic acid is dependent on concentration and temperature. At elevated temperatures lactic acid will form lactide, which is readily hydrolyzed back to lactic acid.
Lactic acid should be stored in a well-closed container in a cool, dry place.

Несовместимости

Incompatible with oxidizing agents, iodides, and albumin. Reacts violently with hydrofluoric acid and nitric acid.

Регуляторный статус

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (IM, IV, and SC injections; oral syrups and tablets; topical and vaginal preparations). Included in medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.