乌龙岭龙眼果皮的PPO特性及活性抑制

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

为探明乌龙岭龙眼贮藏保鲜过程中的褐变问题,以C6H6O2为底物,采用分光光度法研究了底物浓度对龙眼果皮PPO活性的影响规律.采用正交试验方案,分析了不同抑制剂、pH值和温度对乌龙岭龙眼果皮PPO活性的影响.结果表明,龙眼果皮褐变反应的动力学符合米氏方程,米氏常数为0.054 mol.L-1,最大反应速度为1.428×102U.m in-1.适宜的抑制剂可有效延缓龙眼果皮的褐变,保持龙眼质量.在相同条件下,Na2S2O3抑制效果最好.此外,还对影响龙眼果皮PPO活性的因素进行了优化.

Polyphenol oxidase activities were determined speetrophotometrieally at 410 nm with pyrocateehol 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 kinefies of enzymatie browning was aeeordant with Michaelis equation, the KM and Vmax, were 0.054 mol · L^-1 and 1.428 × 102 U · min^-1 , respeetively. Optimal applieation rate of inhibitors eould delay longan periearp 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 influenee factors of longan periearp polyphenol oxidase activity.