Kinetics of Escherichia coli inactivation in frozen aqueous suspensions by high pressure and its application to frozen chicken meat

Abstract

High pressure destruction kinetics of Escherichia coli (ATCC 25922) in frozen and unfrozen aqueous suspensions were evaluated. Test samples were subjected to high pressure (HP) treatment at 200 to 400MPa for 0 to 10min at room temperature (∼20°C). K-type thermocouples were used to monitor sample temperatures. Sample temperature profile analysis indicated that ice phase transitions from Ice I to Ice III were induced in the frozen samples when the applied pressure was above 330MPa. Microbial survival curves indicated the D-values of E. coli associated with frozen samples were lower than those in unfrozen samples. The associated zp values of E. coli in frozen state (zp=196MPa) was lower than in unfrozen state (zp=250MPa) indicating E. coli in the frozen sample to be more pressure sensitive. A six-log reduction in E. coli was achieved in frozen samples after pressure treatment at >350MPa (example: 350MPa, 3min or 400MPa, 1min).