杨桃若干品种及贮藏期间多酚氧化酶活性的变化

目的]为抑制杨桃贮藏与加工过程中发生的酶促褐变提供理论依据。方法]以8种酚类物质作底物,采用分光光度计法测定不同杨桃品种果实及其贮藏过程中多酚氧化酶(PPO)活性的变化情况。结果]5个甜杨桃品种果实中测有PPO活性,该活性均强烈催化焦性没食子酸的氧化反应,但对绿原酸的氧化活性很弱。不同杨桃品种的PPO活性有很大差异,蜜丝甜杨桃PPO对焦性没食子酸的氧化活性明显高于其他品种,而酸杨桃PPO活性极弱。甜杨桃PPO对焦性没食子酸的Km值为3.79~6.80 mmol/L,其Km值因品种不同而异。在果实贮藏期间,3个甜杨桃品种果实中的PPO活性均呈先降再升高而后又降低的变化趋势。结论]在杨桃制品的加工中宜选用酸杨桃、新加坡红杨桃、马来西亚1号杨桃等PPO活性低的杨桃品种作为加工原料,以有利于酶促褐变的抑制。

Change of Polyphenol Oxidase Activity in Some Carambola Cultivars During Storage

Objective] The aim of the research was to provide theoretical base for restrain the enzymatic browning occurred in storage and processing of carambola cultivars.Method] With 8 kinds of polyphenols as the substrate,the change of polyphenol oxidase activity(PPO)in different carambola cultivars and during their storage was determined by spectrophotometer method.Result] The fruits of 5 tested sweet carambola cultivars had PPO activity.All PPO activity could strongly catalyze oxidative activity of pyrogallic acid,but they were very weak for the oxidative activity of chlorogenic acid.There was a great difference on PPO activity among different carambola cultivars.The oxidative activity towards pyrogallic acid in Misi sweet carambola was significantly higher than that in other varieties and the PPO activity in acid carambola was extremely weak.The Km value of PPO of the sweet carambola towards pyrogallic acid was in 3.79～6.80 mmol/L.The Km value varied because of different carambola cultivars.During fruit storage,the PPO activity in fruits of 3 tested sweet carambola cultivars showed such a trend of first ldecreasing then increasing and finally reducing.Conclusion] In the processing of carambola products the carambola cultivars with low PPO such as acid carambola,Singapore red carambola,Malaysia 1 carambola should be selected as processing materials,which favors to restrain the enzymatic browning.