结球生菜多酚氧化酶动力学特性研究

Study on the kinetic character of polyphenol oxidase in iceberg lettuce

为解决生菜加工贮藏过程中出现的褐变问题,研究了结球生菜多酚氧化酶(polyphenol oxidase,PPO)动力学特性,分析了pH、温度及底物浓度等因素对PPO活性的影响,建立了结球生菜褐变的反应动力学方程。结果表明,结球生菜最适pH为8.0,最适温度为40℃。用Michaelis-Menten机理描述可得结球生菜PPO相应的动力学参数Km=0.0691mol/L,vmax=26.5957U/min。生菜叶片组织中的PPO活性较强,叶柄和茎部组织中的PPO活性差异不大,均低于叶片组织中的PPO活性,且结球生菜茎部切口处已经发生褐变的部分PPO活性为6.12U/min,远高于没有发生褐变的部分。

For solving the problem of browning in the process and storage of iceberg lettuce,the Kinetic Character of polyphenol oxidase（PPO）in iceberg lettuce were studied.Analysised the PPO activity in different pH,temperature and substrate concentration,established the kinetic equation of iceberg lettuce browning.The results showed that the optimum pH and temperature of lettuce PPO was 8.0 and 40℃,respectively.The reaction kinetic of enzymatic browning was accordant with michaelis equation,the Km and vmax were 0.0691mol/L and 26.5957U/min,respectively.The PPO activity in iceberg lettuce leaf tissue was very strong,little difference of PPO activity in the organization of petiole and stems,but lower than in the leaf tissue.And the PPO activity was 6.12U/min in iceberg lettuce stems incision which had some browning,much higher than no browning part.