Study On Effects Of Combined Medium Temperature And High-pressure Jet On Food Microorganisms And Quality

High hydrostatic pressure (HHP), the focus in food processing field, can not only kill food-borne microorganisms, but bring less detriment to food compounds such as nutrients, pigments, and flavoring agents, etc.. The processing method of combined medium temperature and high-pressure jet was studied to make HHP industrialization. The effects of pressure, material temperature, pH value and treatment time on the bacteria, polyphenoloxidase (PPO), peroxidase (POD) and ascorbic acid (Vc) were studied respectively. The relationship between the estimation index and the influence factors was discussed, too.Results showed that combined medium temperature and high-pressure jet could evidently promote sterilization effect. With the material temperature of 35℃ and the pressure of 10-80MPa, the death rate arrived the highest at 20MPa. Given the pressure of 20MPa combined with the temperature of 35-55℃, the fatality result at 55℃ was the best. In short, the longer the treatment time, the less the viable bacteria. However, treated for 2min at 50MPa,the sterilization became steady. The survivor of bacteria was the least at pH4.0. PPO can be affected by the combination treatment. At 35℃ and 10-80MPa, the pressure of both 20MPa and 50MPa could activate PPO, while other pressures inactivated it. At 20MPa, the inactivation of PPO was the most striking at 35℃. As time went on, the pressure of 20MPa and 50MPa made PPO activate at first and inactivate later. However, PPO was gradually inactivated at 80MPa. PPO was inactivated most evidently at pH3.0. Combination treatment also affected POD activity. The pressure of 10-40MPa could activate POD, while the pressure of 50~80MPa inactivated it. At 20MPa, the inactivation of POD at 55℃ was the most marked. When the treatment time extended, POD activity was first rise and then drop. The lower the pH value, the stronger the inactivation of POD. The combination treatment could less affect ascorbic acid. The surplus rate of Vc would lower in respond to the increase of pressure, temperature, the treatment time and the acidity. By means of composite experiments, an optimum condition turned out to be the combination of the pressure of 80MPa, the material temperature of 35℃, pH4.0 and the treatment time of 8min.