超高压处理对梨汁中多酚氧化酶活性的影响

Study on Effect of High Pressure Treatment of Fresh Pear Juice on PPO Activity

目的研究鲜榨梨汁中多酚氧化酶(PPO)的活性受高压和热协同处理的影响。方法使用超高压技术单独或协同加热处理加或不加维生素C的鲜榨梨汁,测定其中PPO活性和果汁颜色。结果200～600MPa的压力处理对果汁中PPO活性影响不大,400MPa的压力对PPO有激活作用;高于600MPa的压力使PPO显著失活。维生素C在500MPa以下对果汁中PPO有激活作用,在600MPa以上或热处理结合高压时有钝化PPO的作用。随着保压时间延长和温度升高,梨汁中PPO相对活性逐渐降低。500MPa60℃或750MPa50℃以上的处理条件可使鲜榨梨汁中的PPO失去60%以上的活性,750MPa50℃的处理条件下果汁颜色变化不显著。结论梨的PPO是耐高压的酶。

Objective To study the effect of high pressure alone or combined with heating treatment of fresh pear juice on PPO activity in it.Methods The ultrahigh pressure technology alone or combined with heating was used in the processing of fresh pear juice added VC or not,and then the color of juice and activity of PPO in it was assayed.Results As the pressure used increased,the activity of PPO in juice did not change significantly during the pressure scope of 200MPa￣600MPa and 400 MPa could activate PPO in juice.Effect of pressure on inactiva-tion of PPO became remarkable when pressured above 600 MPa.PPO in juice added VC was activated when pressured below 500 MPa and was inactivated when pressured above 600 MPa or combined with heating.The activity of PPO in juice decreased step by step with the increasing of heating temperature and pressure holding time.The treatment of 500 MPa above 60 ℃ or 750 MPa above 50 ℃ could inactivate PPO by 60% activity and the color change of juice was insignificant under the condition of 750 MPa above 50 ℃(△E was 0.9).Conclusion PPO in pear juice is hardly inactivated by high pressure.