莲藕的酶促褐变及其贮藏中褐变的控制

Enzymatic browning of lotus roots and its control during storage

为有效控制莲藕褐变,试验研究了温度、pH值、底物浓度以及抑制剂对莲藕多酚氧化酶(PPO)的影响。结果表明:莲藕PPO最适pH值为7.5,最适温度为35℃,以邻苯二酚为底物,米氏常数Km为0.0273mol/L。亚硫酸钠、抗坏血酸(VC)对莲藕PPO活性具有较好抑制作用,乙酸、柠檬酸、植酸、木瓜蛋白酶、半胱氨酸也对莲藕PPO活性具有一定抑制作用。0.2%VC+2%乙酸+0.03%亚硫酸钠抑制剂处理对莲藕褐变的抑制效果最佳。可以通过浸泡亚硫酸钠和抗坏血酸(VC)、调节pH值、低温贮藏等方法来抑制莲藕PPO活性,控制莲藕褐变。

Effects of temperature, pH value, substrate concentration and enzyme inhibitors on polyphenol oxidase （PPO） activity in lotus roots were investigated to control enzymatic browning of lotus roots. The results showed that the optimum pH value of PPO activity of lotus roots was 7.5, and the optimum temperature of PPO activity was 35℃. The kinetics of oxidation of pyrocatechol catalyzed by the complexes were studied. The Michaelis constant of o-dihydroxybenzene catalyzed by PPO was as follows： Km=0.0273 mol/L. Treatments of sodium sulfite or VC restrained the PPO activity significantly. Treatments of acetic acid, citric acid, phytic acid, papain or cysteine also restrained the PPO activity. The optimum treatment for controlling enzymatic browning was 0.2% VC ＋2% acetic acid ＋ 0.03% sodium sulfite. Dipping in sodium sulfite and VC, adjusting pH values and storage at low temperature, etc. can be used for inhibiting PPO activity and control enzymatic browning of lotus roots.