Characteristics and activity control of PPO in the pericarp of longan variety Wulongling

Polyphenol oxidase activities were determined spectrophotometrically at 410 nm with pyrocatechol as substrate at different levels.The effects of substrate concentration,pH and temperature on polyphenol oxidase were analysed by orthogonal experiment.The result showed that the reaction kinetics of enzymatic browning was accordant with Michaelis equation,the KM and νmax were 0.054 mol·L-1 and 1.428×102 U·min-1,respectively.Optimal application rate of inhibitors could delay longan pericarp browning efficiently,and keep the quality of longan.At the same reaction condition,sodium thiosulfate produced the best result.Tests were also designed to optimize the influence factors of longan pericarp polyphenol oxidase activity.