Inactivation Of Sublethally Injured Saccharomyces Cerevisiae Induced By PEF And Its Application

Pulsed electric field (PEF) is one of the research focuses in non-thermal processing field,because of its advantages in sterilization and inactivation of enzymes, also the characteristicsof remaining fresh of foods. Early Studies always concerned the effect of PEF on sterilization,inactivation of enzymes and quality of liquid foods. There are limited reports aboutmechanisms, influence factors of recovery, further sterilization methods of sublethalmicroorganism cells and the practical application of these methods. In this study,Saccharomyces cerevisiae was chosen as the object. The influence factors of sublethallyinjured cells recovery, further sterilization methods, mechanisms and the practical applicationof these methods were investigated.Firstly, proper concentration of sodium chloride in selective medium was investigated, aswell as the influence of electric field intensity and treatment time on lethal and sublethal of S.cerevisiae. Results showed that the proper concentration of NaCl was7%(w/w). Proportionof sublethal cells increased first and then reduced with the strengthening of treatment strength.Influence factors of sublethal cells recovery were also studied, including pH, repairtemperature, presence of nutrients and natural preservatives. It indicated that pH andtemperature were both important factors for the repair of sublethally injured cells. Also,effects of nutrients and natural preservatives on recovery process related with pH.Further inactivation methods were also discussed in this study, by studying thesynergistic effect of low temperature (4oC), mild temperature (50oC,55oC), tea polyphenols,natamycin and PEF.In this study, mechanisms of PEF treatment and synergy treatment were investigated bytwo-dimensional electrophoresis. The results showed that both treatment methods couldinfluent the expression of S. Cerevisiae protein, but showed little effect on isoelectric pointand molecular weight distribution of proteins.These pasteurization methods were applied to heat-sensitive cantaloupe juice. Itindicated the feasibility of these methods by evaluating microbiological index and physicaland chemical quality of cantaloupe juice in storage.