Inactivation Kinetics of Polyphenol Oxidase of Fresh-cut Apple by Ultrasonic Treatment

The effects of ultrasonic treatment on inactivation of polyphenol oxidase( PPO) activity of fresh-cut apple were investigated,and inactivation kinetics of PPO was analyzed by using a first-order reaction kinetic under the following experimental conditions: ultrasonic power( 240- 600 W) and ultrasonic temperature( 30- 50 ℃). The results indicated that the optimal temperature of PPO of fresh-cut apple was 30 ℃,and enzyme activity gradually decreased with the increasing heat treatment time. The inactivation of PPO could be significantly affected by the ultrasound of power,processing temperature,and processing time. With the increasing ultrasonic power,temperature and prolonged ultrasonic processing time,the inactivation of PPO became more significant. The inactivation of PPO was fitted well to the first-order reaction kinetic model under the experimental conditions. The k value raised and the D value decreased with the increasing ultrasonic power and processing temperature. Ultrasonic treatment reduced the thermal sensitivity of PPO.