台湾青枣多酚氧化酶特性的研究

采用分光光度法,对台湾青枣多酚氧化酶(PPO)的催化特性、最适波长、最适反应时间、最适温度、最适pH值、热稳定性等性质进行了研究,同时研究了抗坏血酸、柠檬酸、L-半胱氨酸3种添加剂对台湾青枣多酚氧化酶活性的影响,以寻求在果品的保鲜以及果肉初加工过程中抑制PPO活性的各控制手段与果品加工的有机结合方法,为防止褐变提供有效、合理的措施。实验结果表明:以邻苯二酚为反应底物时,台湾青枣多酚氧化酶催化氧化产物的最适波长为420 nm,最佳反应时间为20 min,最适反应温度为30℃,最适pH值为6.8。90℃水浴处理5 min该酶已基本失活。3种抑制剂对该酶均表现出不同的抑制效果。单一抑制剂对台湾青枣多酚氧化酶酶促褐变抑制效果的强弱次序为:L-半胱氨酸>抗坏血酸>柠檬酸。其中L-半胱氨酸的有效抑制浓度为0.100 0%。

Study on Polyphenol Oxidase Properties of Taiwanese Cyan Jujube

The polyphenol oxidase(PPO)properties of Taiwanese cyan jujube were studied with spectrophotometer,including its catalytic characteristics,maximum absorbption wavelength,optimum temperature,optimum pH,thermostability of enzyme and so on.It was also studied the effects of the inhibitors ascorbic acid,citric acid and L-cysteine on the activity of PPO of Taiwanese cyan jujube.When catechol was used as substrate,the results showed that the optimum conditions were as follows:λ=420 nm,pH=6.8,t=30 ℃,the time of reactivity≈20 min for PPO.However,the PPO was inactivated in 90 ℃ water for 5 min.Three kinds of inhibitors had different inhibition effects on PPO activity.The anti-browning effect sequence of single inhibitors was L-cysteine> ascorbic acid> citric acid.The effective concentration of inhibitor L-cysteine was 0.100 0%.