Sterilization Effect Of Instantaneous High Pressure And Its Dynamics Model

The earlier research had found that the Microfluidizer had good material sterilizing effect in the crush course. But nobody has systemically researched its sterilization mechanism and effect. We named this treatment form as 'Instantaneous high-pressure (IHP)' to get rid of the restriction of equipment. This concept was put forward on the basis of the practical researches about the sterilization technology of the Microfluidizer and the theoretical researches about the sterilization mechanism. This concept is theoretical generalization of the sterilization technology which stressly reflects the material passes through the equipment quickly, the last time is very short(less than 1×10~-3)and the changing rate of pressure is very huge. During this process, the microorganism is affected by high-speed impaction, vortex, sudden pressure drop, and concomitant rising of temperature, etc.The yeast,E.coli and B.sbutilis were taken as the research objects for discussing the sterilizing effect of IHP. It was found that IHP had obvious sterilizing effect to yeast; E.coli and B.subtilis. But the effect to B.subtilis was relatively weaker due to the resisting of the spore. At room temperature(25℃) under pressure 120MPa and single pass,the death rate of yeast, E.coli and B.subtilis were 99.89%,99.35%,93.82% respectively. IHP yielded two destroying forms to the microorganism, the direct crash and biological effects. For yeast, both forms existed, but for E.coli and B.subtilis, the biological effect contributed the most. Moreover the lethal action to microorganisms was irreversible. During the process, experiment dates showed that along with the increase of process pressure and passes, the lethal effect to these microorganisms became much stronger. Besides this, the rising of feed-in temperature was also favor of improving the sterilizing effect. However, the influencing factors like feed-in temperature, process pressure and passes had varied destroying effects for these microbes.Taking B.subtilis as subject, research about the influence of basic components in food to the sterilizing effect of IHP was done. The result proved that the sterilizingeffect was higher in acidic or alkaline condition, protein and saccharides had protecting action to microbes, with higher concentration reaching stronger protection. Regression composite design was applied in this thesis. Effect of feed-in temperature, pressure and passes on the lethal effect to B.subtilis was investigated. The dynamic model of the lethal effect to B.subtilis drawn from the test dates displayed as:Y = 95.374+0.518X1+2.551X2+3.551X3-0.86X2X3-0.362X22-0.524X32 By the analysis of variance, the passes is the most influential factor, while pressure comes next and the feed-in temperature has the least influential effect.Through analysis of responding surface methodology(RSM) for the dynamic model, the result showed that the lethal effect in the area of high temperature and high pressure is higher than that in the area of low temperature and low pressure. Pressure and temperature have a certain extent coordinated effect in sterilization. Thus the sterilizing effect could be increased by the control of temperature and pressure. Finally the model was tested feasible.