High-pressure Processing: Kinetic Models for Microbial and Enzyme Inactivation

High pressure processing (HPP) has become the most widely accepted nonthermal food preservation technology. The pressure range for commercial processes is typically around 100-600 MPa, whereas moderate temperature (up to 65°C) may be used to increase microbial and enzymatic inactivation levels. However, these industrial processing conditions are insufficient to achieve sterilization since much higher pressure levels (>1000 MPa) would be required to inactivate bacterial endospores and enzymes of importance in food preservation. The next generation of commercial pressure processing units will operate at about 90-120°C and 600-800 MPa for treatments defined as Pressure Assisted Thermal Processing (PATP), or Pressure Assisted Thermal Sterilization (PATS) if the commercial food sterilization level required is achieved. Most published HPP kinetic studies have focused only on pressure effects on the microbial load and enzyme activity in foods and model systems. Published work on primary and secondary models to predict simultaneously the effect of pressure and temperature on microbial and enzymatic inactivation kinetics is still incomplete. Moreover, few references provide a detailed and complete analysis of theoretical, empirical, and semi-empirical basis for the kinetic models proposed to predict the level of microbial and enzyme inactivation achieved. This review organizes these published kinetic models according to the approach used, and then presents an in-depth and critical revision to define the modeling research needed to provide commercial users with the computational tools needed to develop and optimize pasteurization and sterilization pressure treatments.Keywords: Primary and Secondary Models, High Pressure Processing, Kinetics, Microbial Inactivation, Pressure Assisted Thermal Processing, Enzyme Inactivatio

Monte Carlo analysis of the product handling and high-pressure treatment effects on the Vibrio vulnificus risk to raw oysters consumers

A Monte Carlo procedure considering the variability in oyster handling from harvest to raw consumption estimated reductions in the number of Vibrio vulnificus induced septicemia cases achieved by high-pressure processing (HPP). The calculations yielded pathogen load distributions in raw oysters from harvest to consumption. In the warm season, 2-6 min treatments at 250 MPa and 1°C would lower the predicted number of septicemia cases associated with raw oyster consumption from 4,932 to less than four per 100 million consumption events (95% confidence). This study highlighted that HPP conditions should be selected according to the seasonal pathogen load and environment temperature. Finally, the procedure emphasized that the variability in the V. vulnificus population at harvest, before and after HPP treatments, reflecting in part the microbiological quantification methods used, significantly affected the estimated number of septicemia cases. Therefore, improving microbiological quantification should provide better predictions of the number of septicemia cases.Keywords: Beta-Poisson dose response models, Monte Carlo analysis, Vibrio vulnificus, Oyster, High pressure processing, Seafood poisoning ris