IN-VITRO ENZYMATIC OXIDATION OF APPLE PHENOLS

4-methylcatechol and (-) epicatechin hew been found to be the most imp ortant phenols, contributing towards browning due to their synergic ef fect in enzymic oxidation of the other phenols of apples. Initially, c hlorogenic acid and caffeic acid play a role towards browning, but in later stages, (-] epicatechin contributes towards browning significant ly. These catalyse the enzymic oxidation of procyanidin B-2, which ici a non-substrate for polyphenol oxidase and also catalyse the hydroxyl ation of phloretin, to form hydroxyphloretin, which is further enzymat ically oxidised. 2,4-dihydroxybenzoic acid has been found to be an eff ective inhibitor of polyphenol oxidase-mediated oxidation of () epicat echin, whereas p-coumaric acid inhibits oxidation of (-) epicatechin, 4-methylcatechol and chlorogenic acid.