(1) Extraction of immature apples, grapes, peaches and other fruit juices to boil, add lime water, produce calcium salt precipitation, and then after treatment to produce free malic acid.
(2) The synthesis method catalyzes benzene to obtain maleic acid and aristolochic acid, which are then combined at high temperature and pressurized water. The conditions for hydration reactions are usually in 180-220 ' C and 1. 411. Reaction 3-5h under 8MPa pressure.
The reaction products are mainly malic acid and a small amount of anti-butene acid, regulating the content of malic acid in 40~c is 40% and cooling the solution to about S ' C, filtering the separation of anti-maleic acid crystals, mother liquor concentration, centrifugal separation of solids, coarse malic acid, and then refined crystallization of the finished product.
(3) The fermentation method uses the enzyme fermentation to produce the left-spun malic acid from the anti-butene acid.