A comparative study of inactivation of peach polyphenol oxidase and carrot polyphenol oxidase induced by high-pressure carbon dioxide

The inactivation of polyphenol oxidase (PPO) in peach juice and PPO in carrot juice was investigated by high-pressure carbon dioxide (HPCD), and their inactivation kinetics was analysed and compared. The temperature was 35-55 degrees C, the pressure was 5-15 MPa under HPCD condition. Results showed that HPCD enhanced the inactivation effect of the temperature on the two PPOs. The inactivation kinetics of peach PPO was well fitted to a first-order kinetic model, of carrot PPO to a fraction-conversion model as a function of temperatures or pressures. Susceptibility of the rate constant k of peach PPO was not altered and of carrot PPO was lessened to the temperature, but the susceptibility of the rate constant k of peach PPO and carrot PPO to the pressure was not changed when the pressure was >8 or 12 MPa, indicating the presence of a threshold pressure.