Abstract: This paper studied the effect of instantaneous high pressure(IHP) treatment on polyphenoloxidase activities under different conditions. The results demonstrated that: IHP effectively reduced the activities of polyphenoloxidase. If polyphenoloxidase was treated separately at 25, 35 and 45℃ with pH6, its activity decrease was quick for treating pressure at 0.1～100MPa and slowed down while surpassing 100MPa. Increasing feed-in temperature can augment the reduction of activities of polyphenoloxidase being treated by IHP. At pH4.5 and 25℃, polyphenoloxidase was processed 3 times under 120,140 and 160MPa respectively, and the results showed that under the same pressure, the activity of polyphenoloxidase decreased with processed times, and the decrease extent also became smaller with processed times. Under common atmospheric pressure, polyphenoloxidase was fairly stable when pH was between 4.5～6.5, and its stability is tremendously undermined below pH4.5; when the process pressure was 140MPa, the activity of polyphenoloxidase was lower than that under atmospheric pressure, and furthermore the activity decrease was more obvious under strong acidic condition, while the decrease under strong alkaline condition followed with the smallest decrease being witnessed at pH4.5. By detecting the fluorescence intensity of tyrosine and tryptophan we found that the IHP treatment indeed altered the structure of PPO. But there was no specific corelation between PPO activity and fluorescencei ntensity.

Key words:  , instantaneous high pressure (IHP)； polyphenoloxidase；