What is the difference between malic acid and L-malic acid?

Malic acid and L-malic acid are essentially the same compound; however, the difference lies in their molecular structure and usage.

Malic Acid: 

This term typically refers to a mixture of both L-malic acid and its mirror image, D-malic acid. This mixture is known as racemic malic acid. Racemic malic acid is commonly found in nature and is used in food and beverage industries as an acidulant to add a sour taste.

L-Malic Acid

This is the specific stereoisomer of malic acid, where the molecule has a left-handed orientation. It is also naturally occurring and is often the form found in living organisms. L-malic acid is a key intermediate in the citric acid cycle, which is the primary metabolic pathway used by cells to generate energy. It is also used in the food industry as an acidulant, flavor enhancer, and preservative.

L-malic acid

In summary, while malic acid can refer to the mixture of L-malic acid and D-malic acid, L-malic acid specifically refers to the left-handed stereoisomer, which is biologically significant and commonly used in various applications.