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The National Agricultural Library is one of four national libraries of the United States, with locations in Beltsville, Maryland and Washington, D.C. It houses one of the world's largest and most accessible agricultural information collections and serves as the nexus for a national network of state land-grant and U.S. Department of Agriculture field libraries. In fiscal year 2011 (Oct 2010 through Sept 2011) NAL delivered more than 100 million direct customer service transactions.


Written Paper

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