Synergistic Inactivation Effect Of High Pressure And Temperature And Related Kinetic Studies

The combination of high pressure and temperature treatment can solve the contradiction between quality and safety in the food sterilization process,and it is an international frontier hot spot in food science research now.This research studies the temperature change of frozen samples under high pressure,explores the high pressure and low temperature sterilization mechanism under different substrates,and establishes the pressure-temperature collaborative kinetic model.In the field of high pressure and moderature temperature inactivation of spores,the inactivation kinetics of high pressure and moderature temperature was explored,and a multi-dimensional dynamic model of high pressure and moderature temperature inactivation was established.Main results are as follows:1.The container designed in this study can keep the frozen samples at low temperature?subzero?under high pressure without cooling the whole pressure system.Temperature control?±1??in high pressure and moderature temperature experiments was confirmed.The temperature control and detection can support the establishment and accuracy of bactericidal kinetic model.2.The inactivation effect of pulse anad static hold high pressure treatment can be improved by phase transition and changing sample state?frozen?.Injured Escherichia coli cells were observed in unfrozen and frozen suspension and bayberry juice after various high-pressure treatment conditions.We should recognize that overestimation of survival reductions could result from enumerating on selective medium,especially under high pressure-subzero temperature treatment condition.According to the results of transmission electron microscopy,the effects of high pressure treatment on E.coli in frozen samples and unfrozen samples are different.When high pressure is 330 MPa,the phase change of ice I and ice III is the main reason for cell damages.3.E.coli inactivation in frozen carrot juice of static hold high pressure treatment followed the first order rate kinetics.When the pressure is greater than 280 MPa,the phase transition,pressure level and state of the sample contribute to the better inactivation of E.coli in frozen carrot juice,especially the transition of ice I and ice III.The inactivation effect of multiple pulse high pressure treatment on E.coli in frozen carrot juice also followed the first order rate kinetics.Compared with static high pressure treatment,multiple pulse high pressure treatment of frozen samples can shorten the total processing time and improve the processing efficiency.4.The combination of high pressure and moderature temperature treatment has synergistic inactivation effect and can reduce the pressure and temperature level.The inactivation kinetics of high pressure and moderature temperature treatment on Geobacillus stearothermophilus in carrot juice was conformed to the first-order kinetic model(R²_Adj>0.913).The Ea value of thermal inactivation is 371.3 kJ/mol.At pressure of 200⁶00 MPa combined with different moderature temperatures,the Ea values are 61.7⁸7.6 kJ/mol.They are lower than heat treatment alone due to the synergistic effect of pressure and temperature.5.At constant pressure,Z_T model is well fitted.But at constant temperature,Z_P model of is depended to the pressure and temperature interval.G.stearothermophilus is sensitive to temperature but not to pressure at low pressures?200⁴00 MPa?.In this study,a three-dimensional kinetic model of G.stearothermophilus in carrot juice treated by high pressure and moderature temperature was established,logD=2.1315673+0.0017047×?P-P₀?-0.0101146×T-0.0000037×?P-P₀?²+0.0000079×?P-P₀?×T-0.0001235×T²,R² value is 0.968.6.The synergistic inactivation kinetics of G.stearothermophilus in carrot juice under high pressure and moderature temperature also conforms to the Weibull model(R²_Adj>0.953).When using first-order kinetic model or Weibull model from carrot juice to predict the inactivation effect of high pressure and moderature temperature on chicken broth or piece of meat,the predict values may underestimated or overestimated.It demonstrates that the same model cannot be applied directly to different systems.