Lactic Acid
The short version
The natural acid of sour milk — a mild, ubiquitous acidulant and preservative.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Where it comes from
First isolated by Carl Scheele in 1780 from sour milk — hence the name. Produced industrially today primarily by bacterial fermentation of sugars (Lactobacillus species), as well as by chemical synthesis from lactonitrile.
How it's used
Used in yogurts, pickles, salad dressings, cured meats, and infant formula. Provides tartness, controls pH, and acts as a mild preservative. Commercially important as a building block for biodegradable plastics.
Safety profile
No ADI required — naturally occurring central intermediate in human metabolism. GRAS in the US. Infants under 3 months should not receive D-lactic acid due to limited metabolic capacity; food-grade is typically L- or DL-isomer.
Physical & chemical properties
Colorless to pale yellow syrupy liquid (commercial 80–88% solution). Miscible with water. Weak acid (pKa 3.86). Hygroscopic. Optically active in pure isomers.
Regulation worldwide
Permitted globally without restrictive limits. Specific guidance restricts D-lactic acid in infant foods.
Educational information only. Not medical or dietary advice.