What Is Malic Acid?
Malic acid, also known as hydroxy succinic acid, is an organic acid with the chemical formula C4H6O5. It possesses one asymmetric carbon atom, leading to the existence of optical isomers.
The naturally occurring form of malic acid is the L-form, commonly found in fruits like grapes and apples. Malic acid can be produced through the reduction of L-tartaric acid with hydrogen iodide or by the action of fumarase on fumaric acid.
Physicochemical Properties of L-Malic Acid
1. Name
English name: L-malic acid
IUPAC name: (2S)-2-hydroxybutanedioic acid
2. Molecular Formula
C4H6O5
3. Molecular Weight
134.09
4. Melting Point
100°C (L-form)
5. Solvent Solubility
Easily soluble in water and alcohol.
Characteristics, Bioactivity, and Uses of Malic Acid
1. Uses as a Food Additive
Malic acid, known for its refreshing sour taste, is used as an acidulant in foods and beverages. It has inherent bactericidal properties, which are enhanced when combined with other organic acids. Consequently, it’s being explored as a food additive with potential bactericidal effects. In the food industry, malic acid is used as a pH adjuster, emulsifier, and is most commonly utilized in its racemic form.
2. Use in the Cosmetic Field
In the cosmetic industry, malic acid is used in toothpaste for its plaque and tartar prevention properties and as a pH adjuster in shampoos, due to its buffering properties. Low pH shampoos containing malic acid, combined with anti-inflammatory agents, have been reported to be effective for scalp care.
3. Industrial Applications
Malic acid’s chelating properties enable it to form complexes with metal atoms, making it useful as a metal surface cleaning agent.
4. Role as a Citric Acid Cycle Intermediate
Malic acid is an intermediate in the citric acid cycle, being converted to oxaloacetic acid by malate dehydrogenase. It plays a crucial role in the energy metabolism of aerobic organisms.
Foods With High Malic Acid Content
Fruits such as apples and grapes are rich in malic acid.