lactic acid

noun

: a hygroscopic organic acid C₃H₆O₃ present normally especially in muscle tissue as a by-product of anaerobic glycolysis, produced in carbohydrate matter usually by bacterial fermentation, and used especially in food and medicine and in industry

Examples of lactic acid in a Sentence

Recent Examples on the Web

This formula features a blend of potent chemical exfoliants, including glycolic acid, lactic acid, tartaric acid, citric acid, and salicylic acid, to target excess oil production, dull skin, and hyperpigmentation. —Jessie Quinn, Peoplemag, 25 Mar. 2024

Those two new components—lactic acid and diacetyl—make buttermilk an MVP in waffles and pancakes. —Karla Walsh, Better Homes & Gardens, 22 Mar. 2024

Youth to the People 10% AHA + Yerba Mate Smoothing Energy Body Scrub, which combines AHAs and olive seed powder, and Sunday Riley Charcoal Smoothie, which uses salicylic acid and lactic acid plus biodegradable wax are two standouts. —Hannah Baxter, Allure, 5 Mar. 2024

Yogurt is made by combining heated milk and bacteria, which begins the fermentation process and converts the sugar in milk to lactic acid and allows the milk to thicken and become tart. —Clare Mulroy, USA TODAY, 25 Feb. 2024

Other helpful ingredients include willow bark to manage excess oil, lactic acid to exfoliate, along with vitamins A, C, E, Coenzyme Q10, and antioxidants to nourish skin. —Chaunie Brusie, Rn, Parents, 26 Feb. 2024

That culture then produces lactic acid, which causes the milk protein to thicken into a creamy, slightly tart mixture. —Genevieve Ko, San Diego Union-Tribune, 21 Feb. 2024

This helps balance out the formula’s lactic acid, an exfoliator that can help reduce the appearance of pores and fine lines. —Macaela MacKenzie, Glamour, 17 Feb. 2024

Key ingredients: 10% glycolic and lactic acids, pumice buffing beads, vitamin E | Base: Beads | Size: 8 oz. —Alyssa Brascia, Peoplemag, 16 Feb. 2024

Word History

First Known Use

1790, in the meaning defined above

Kids Definition

lactic acid

noun

lac·​tic acid

ˌlak-tik-

: an organic acid present especially in muscle tissue as a result of the breakdown of carbohydrates (as glycogen), is made from carbohydrates usually by fermentation by bacteria, and is used especially in food and medicine

Medical Definition

lactic acid

noun

: a hygroscopic organic acid C₃H₆O₃ that is known in three optically isomeric forms:

a

or D-lactic acid

ˈdē- 

: the dextrorotatory form present normally in blood and muscle tissue as a product of the anaerobic metabolism of glucose and glycogen

b

or L-lactic acid

ˈel- 

: the levorotatory form obtained by biological fermentation of sucrose

c

or DL-lactic acid

ˈdē-ˈel- 

: the racemic form present in food products and made usually by bacterial fermentation (as of whey or raw sugar) but also synthetically, and used chiefly in foods and beverages, in medicine, in tanning and dyeing, and in making esters for use as solvents and plasticizers