effect of anti browning agents on partial purified polyphenol oxidase of hawthorn (crataegus spp

objective: polyphenol oxidase or ppo (ec 1.14.18.1) is considered the enzyme responsible for quality deterioration and browning in different fruits during postharvest period. the objective of this study was to evaluate the antibrowning (inhibition of polyphenol oxidase activity) effect of cysteine, ascorbic acid, citric acid, kojic acid and glycine at two different ph (6 and 7) in  hawthorn. methods: partial purified polyphenol oxidase was mixed with cys, ascorbic acid,  citric acid, glycine and kojic acid, to assess their effect on ppo. results: the most effective ppo inhibitors was kojic acid. ic50 for cysteine was earned 0.48 and 0.58, for ascorbic acid, 0.8 and 1, for citric acid, 0.75 and 0.85 and for kojic acid was 0.3 and 0.4 at ph 6 and 7, respectively partial purified polyphenol oxidase was mixed with cys, ascorbic acid,  citric acid, glycine and kojic acid, to assess their effect on ppo. the most effective ppo inhibitors was kojic acid. ic50 for cysteine was earned 0.48 and 0.58, for ascorbic acid, 0.8 and 1, for citric acid, 0.75 and 0.85 and for kojic acid was 0.3 and 0.4 at ph 6 and 7, respectively.