Effect of Ultra High Pressure Treatment on Bacterium and Polyphenol Oxidase of Apple Juice

The paper systematically studied the residual activities of enzymes and sterilization of apple juice under different treatment pressure and treatment time.The results showed that the number of bacteria count,coliform group and polyphenol oxidase(PPO) activity decreased significantly as the treatment pressure and time was increased.The total bacteria count decreased from 9 750 cfu/mL to 80 cfu/mL,the coliform group reduced from 30 cfu/mL to 0 cfu/mL,the PPO was inactivated completely and the loss of VC below 20 % at 400 MPa for 25 min treatment.Experimental results reached the safety standards of Food and Drug Administration on fruit and vegetable juice non-thermal processing and National Standard on cold drink food safety.