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Recent advances in chemistry of enzymatic browning: an overview  [1995]

Whitaker, J.R. (University of California, Davis, CA.) Lee, C.Y.

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Polyphenol oxidase (PPO) is important in the beneficial coloration of some of our foods, such as prunes, dark raisins and teas. However, in most cases, PPO is the most damaging of enzymes in color deterioration (browning) of plant foods, with resulting losses of up to 50% for tropical fruits and others. Preventing PPO activity in postharvest fruits and vegetables has enormous economic and quality benefits, but current prevention methods are not ideal. Through an understanding of the structure and mechanism of action of PPO, and the chemistry of enzymatic browning, better prevention methods can be used, including decrease in PPO biosynthesis in vivo by the antisense RNA method. PPO can be used commercially in the biosynthesis of L-DOPA for pharmaceutical uses and for production of other polymeric products. PPO is stable in water-immiscible organic solvents, facilitating specific oxidation reactions with water-insoluble organic compounds. Melanins for use as sun blockers can be produced readily by PPO genetically engineered into Escherichia coli