- CAS # 598-82-3 (racemate), 79-33-4 (L), 10326-41-7 (D)
- FW 90.08 g/mol
- Solubility completely miscible with water
- pKa 3.86
Lactic acid is ubiquitous in nature. It is one of the rare cases where both optical isomers are found naturally. L-(+) lactic acid is found in primate blood, sweat, muscle, and bile. D-(−) lactic acid together with its L-(+) relative can be found in milk products like yoghurt, kefir, or cottage cheese, as well as in sour-dough bread, and is also a product of the anaerobic fermentation that leads to silage.
Lactic acid is industrially produced on a huge scale, because it is one of the easiest microbiological processes to industrially replicate, and many organic materials can be used for it. The resulting product is “natural” and usually is food grade L-(+) lactic acid, the more desirable isomer. Industrially, often no distinction is made between the D- and L- isomers.
Lactic acid is useful in wine-making to control acidity. It has a harmonic sour taste, but when used too much, can lead to a sauerkraut note in wine.