Malic acid, also known as 2-hydroxysuccinic acid, has two stereoisomers due to an asymmetric carbon atom in the molecule. In nature, it exists in three forms, namely D-malic acid, L-malic acid and its mixture DL-malic acid, which are white crystals or crystalline powder, have strong hygroscopicity, and are easily soluble in water and ethanol. Malic acid has three isomers: L-malic acid, D-malic acid and DL-malic acid. The naturally occurring malic acid is L-shaped and is present in almost all fruits, with the most in pome fruits. Malic acid is colorless needle crystal, or white crystal powder, odorless, with a pungent refreshing and sour taste,
The most common is the levorotatory form, L-malic acid, found in the sap of immature hawthorn, apple and grape fruit. It can also be obtained by biological fermentation of fumaric acid. It is an important intermediate product in the internal circulation of the human body and is easily absorbed by the human body. Therefore, it is widely used in the fields of food, cosmetics, medical and health care products as a food additive and functional food with excellent performance. The racemate can be prepared by fumaric acid or maleic acid under the action of catalyst under high temperature and high pressure and steam action.
production method
The production method of L-malic acid has been developed from the early single extraction method to the following methods: extraction method, chemical synthesis method, one-step fermentation method, two-step fermentation method, immobilized enzyme or cell transformation method. At present, the existing problem is still the lack of good production strains. While researching and breeding good strains, it is necessary to strengthen the research on extraction technology and other related technologies, and it is very necessary to do a good job in the research and development of supporting technologies for upstream and downstream projects.
prepare
(1) Extraction method: Boil the juice of unripe apples, grapes, peaches, etc., add lime water to form calcium salt precipitation, and then process to generate free malic acid.
(2) Synthesis method: benzene is catalytically oxidized to obtain maleic acid and fumaric acid, which are then hydrated under high temperature and pressure. The conditions of the hydration reaction are usually 3-5h at 180-220°C and 1.4-1.8MPa pressure. The reaction product is mainly malic acid and a small amount of fumaric acid, adjust the content of malic acid at 40°C to 40% and cool the solution to about 15°C, filter and separate fumaric acid crystals, concentrate the mother liquor, and centrifuge. Solid, crude malic acid is obtained, and then refined and crystallized to obtain the finished product.
(3) Fermentation method: L-malic acid is produced by biological enzyme fermentation from fumaric acid.
storage and transportation
This product is packaged in a cardboard drum lined with double-layer food-grade polyethylene plastic bags. This product has the properties of easy moisture absorption and oxidation. It should be covered during transportation and should not be mixed with toxic, odorous and colored powders. Store in a cool and dry place , in a dry warehouse, avoid the sun.
