Effect of ultra high pressure-pH synergistic treatment on the inactivative effect of two enzymes in hami melon juice
In order to investigate the influence of pH,Ultra～High Pressure and pH～ultra high pressure synergistic treatment on the activities of peroxidase(POD) and Polyphenoloxidase(PPO) in hami melon juice,the UHP treatment was carried out using a UHP unit(0.1～500 MPa),temperature(20～60 ℃),holding time(0～40 min),and different pH value(adjusted by citric acid and sodium carbonate:2～11).It was indicated that the optimum pH value ranges of POD and PPO were 6.0～8.0 and 7.0～8.0,respectively.The optimum temperature was 35 ℃ and 30 ℃.It is very difficult to inactivate POD and PPO by simple ultra～high pressure treatment.However,pH～ultra high pressure synergistic treatment proved to efficiently induce enzyme inactivation.The experimental data followed first～order reaction kinetics under the following experimental conditions:pH4、5,temperature 25 ℃,55 ℃,pressure 300～500 MPa and holding time 5～30 min.