Malic acid
China [CN] Malicacid, also known as hydroxysuccinic acid, has three types due to the presence of an asymmetric carbon atom: L-malic acid, D-malic acid, and DL-malic acid. L-malic acid is a product of the tricarboxylic acid cycle in the human body, so the human body can only metabolize L-malic acid. L-malic acid is naturally present in fruits such as apples, grapes and lemons. If extracted from fruits, the content is low and the cost is high, making it impossible to produce on an industrial scale. Only DL-malic acid can be produced by the catalytic synthesis of fumaric acid. Since the human body cannot metabolize DL-malic acid, although DL-malic acid is allowed as a food additive in Europe and America, people always have a sense of insecurity. All malic acid produced by microbial methods is L-malic acid. Therefore, all the malic acid currently in use is produced by microorganisms. In the fields of food and medicine, L-malic acid has basically replaced DL-malic acid.
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