苹果多酚氧化酶的提取及其抑制作用的研究

The Extraction and Inhibition of Apple Polyphenol Oxidase

以冷冻丙酮制备苹果多酚氧化酶(PPO),通过以邻苯二酚为底物测定氧化产物的方法,对苹果果肉中多酚氧化酶的pH值、温度、热稳定性及抗氧化剂抑制作用进行了研究。结果表明:用真空冷冻干燥得到的酶粉能更好的保持多酚氧化酶活性;酶氧化邻苯二酚的最适pH为6.0,最适温度为25℃;PPO在20-25℃时对热较稳定,期后随着温度升高后,酶活迅速降低;在100℃维持1min酶全部失活;抗坏血酸和黄酮类物质能明显地抑制酶促褐变。

Apple polyphenol oxidase（PPO） was extracted with cold acetone and treated with freezing dry. The characteristics of PPO were investigated by determining oxidative product using catechol as substrate. The results showed that vacuum freeze drying for enzyme preparation was better to keep the activity of PPO. The optimal reactive temperature and pH value of PPO were 25 ℃ and 5.0. It was also found that PPO was stable in the range of from20℃ to 25℃. Further increase in temperature, however, decreased its activity. Heated at 100℃ for 60 s, the activity of PPO was almost lost. Ascorbic acid and flavone could significantly inhibit the browning reaction catalyzed by the PPO. The enzymatic activity decreased with the increase of storage time at 25℃ and 4℃, and the activity can keep higher at relatively lower temperature.