Lactic acid is used in foods to add tartness and as a preservative. The name comes from the Latin word for milk, but most lactic acid is produced commercially from corn fermentation.
Lactic acid is what gives the sour taste to spoiled milk, and to sauerkraut.
Lactic acid is also used as a preservative in foods like spanish olives.
lactic acid: InChI=1/C3H6O3/c1-2(4)3(5)6/h2,4H,1H3,(H,5,6)