Polyphenoloxidaseactivityintea,appleandptato英语论文.doc

Polyphenol oxidase activity in tea, apple and potato Mao YuLin College of Agriculture Biotechnology, Zhejiang University, Hangzhou 310058, China Correspondence: 3110100490@zju.edu.cn Words: 1278; Figures: 4Abstract Background Polyphenol oxidase exists in most of plants, changes plants colors, and thus decreases food quality. Therefore, finding the main factors that impacts the PPO is benefit to store food from plants. Methods The content of enzyme in tea leaves, apple fruits, and potato tubers was measured by Folin- phenol method. The main influence factor of PPO activity was determined by orthogonal method. Results The protein yields of the crude enzymes extracted from tea, apple, and potato were 44.318 mg/g, 38.626 mg/g, and 52.114 mg/g, respectively. Tea leaves showed the highest PPO activity at 8 mM catechol, 20oC, and pH 6.5. Apple fruits showed the highest PPO activity at 8 mM catechol, 20oC, and pH 5. Potato tubers showed the highest PPO activity at 20 mM catechol, 30oC, and pH 6. Conclusion The activator and inhibitor are the main factors that are in control of PPO.Temperature is the second important factor and is easy to control. Therefore, we should inhibit PPO activity by controlling storing temperature. Tea and potato could be stored at 40℃, and apple should be stored below 20 oC. Key words: Polyphenol oxidase; Orthogonal method; Activator and inhibitor; Temperature Introduction Polyphenol oxidase (PPO) catalyzes polyphenols to quinones. PPO widely exists in various plants, and plays roles in plant growth and development, and plant adaptability to the environment. Importantly, PPO activity results in brown reactions in plant tissues, and affect the color and quality of the food derived from plants (Kong et al., 2011). Tea, apple, potato are common food and easily available, and contain abundant PPO. A recent study compared PPO activities in fresh tea, apple and potato (L.J.Song et al., 2009). This study used the same methods to extract crude