Study on parameters of heating-inactivation of PPO in pear during processing of cloudy pear juice

The parameters (temperature and time) of heating treatment of pear juice (with or without anti-browning agents) and pear puree to completely or partly inactivate the polyphenoloxidase (PPO) in them were studied. When pear juice was heated at 90℃ for more than 10s,the PPO in it was completely inactivated,but for pear puree the heating time was more than 15s. When pear juice with anti-browning agents was heated at 90℃ for more than 10s,the PPO in it was also completely inactivated. In addition,though heating of pear juice with anti-browning agents at 80℃ for more than 30s did not completely inactivate the PPO in it,enzymatic browning would not occur because of the anti-browning agents added and the low pH of the juice. Heating pear juice at 70℃ for 40s could not prevent enzymatic browning in it.