Traits
Malic acid has three isomers: L-malic acid, D-malic acid and DL-malic acid. Naturally occurring malic acid is L-shaped and is found in almost all fruits, most commonly in pome fruits. Malic acid is colorless needle crystals or white crystal powder, odorless, with a pungent and refreshing sour taste, melting point 127-130ºC, easily soluble in water, 55.59/100mL (20ºC), soluble in ethanol, insoluble in ether . It is hygroscopic, and the pH value of 1% (mass) aqueous solution is 2.4.
(1)D-malic acid:
Density 1.595, melting point 101ºC, decomposition point 140ºC, specific optical rotation +2.92° (methanol), soluble in water,
Methanol, ethanol, acetone.
(2)L-malic acid:
Density 1.595, melting point 100ºC, decomposition point 140ºC, specific optical rotation -2.3° (8.5g/100ml water), easily soluble in water, methanol, acetone, dioxane, insoluble in benzene. Equal amounts of left- and right-handed compounds are mixed to form a racemate. Density 1.601; melting point 131-132ºC, decomposition point 150ºC; soluble in water, methanol, ethanol, dioxane, acetone, insoluble in benzene.
The most common is the levorotatory form, L-malic acid, found in the juice of immature hawthorn, apple and grape fruits. It can also be obtained from fumaric acid through biological fermentation. It is an important intermediate product of the human body's internal circulation and is easily absorbed by the body. Therefore, it is widely used in food, cosmetics, medical and health products and other fields as a food additive and functional food with excellent performance. The racemate can be prepared from fumaric acid or maleic acid under the action of a catalyst under high temperature, high pressure and water vapor.
Application
DL-Malic acid can be used as an acidulant in cool drinks (including lactobacillus drinks, milk drinks, carbonated drinks, cola), frozen foods (including sherbet and ice cream),processed foods (including wine and mayonnaise). It is used as color-keeper and antiseptic of juice. It is also used as emulsion stabilizer of egg yolk. DL-Malic acid also can be used as pharmaceutical intermediate, cosmetic,rinse, metal cleaner, buffering agent, retarder in textile industry, fluorescent whitening agent of polyester fibre.
| Title of index |
index |
| Assay( C4H6O5): |
99.0%~100.5% |
| Specific Rotation[α]D25ºC: |
-0.10°~+0.10° |
| Arsenic(as As): |
≤2mg/kg |
| Lead(as Pb): |
≤2mg/kg |
| Residue on Ignition: |
≤0.1% |
| Fumaric acid: |
≤1.0% |
| Maleic acid: |
≤0.05% |
| Water-insolublematter: |
≤0.1% |
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