Effect of package dimensions and food product properties on non-uniformity of microbial inactivation during high-pressure high-temperature (HPHT) process: a numerical study

Inactivation of micro-organisms during High-Pressure High-Temperature (HPHT) process has become a widely researched topic, especially since Pressure Assisted Thermal Sterilization (PATS) was accepted by the US FDA for commercial production of shelf-stable low-acid foods. Non-uniformity of microbial inactivation may arise due to the non-uniformity of temperature developing within foods during HPHT process. Therefore, from the commercial point of view, the temperature distribution during the process should be kept as uniform as possible. The objective of this study was to numerically investigate the effect of thermal and physical properties of food products, package dimensions, and adiabatic compression heating values of both food and packaging material, on the temperature distribution within foods subjected to HPHT process, and their impacts on the non-uniformity of microbial inactivation. The commercial software COMSOL® Multiphysics was used to numerically predict the distribution of temperature and the inactivation of Clostridium botulinum, an indicator for microbial safety. Coefficient of variation (COV) in microbial inactivation was used to quantify the non-uniformity of the process. Our results showed that increasing the radius of package for a solid food resulted in significantly higher process non-uniformity, in terms of COV in final microbial count. In a liquid food, the mixing effect inside the package due to natural convection could change the non-uniformity of microbial inactivation, which strongly depended on the viscosity of the food product. In addition, increasing the adiabatic compression heating value would aggravate the process non-uniformity for both solid and liquid foods. Dividing a large package into multiple small ones could facilitate the mixing effect of natural convection; therefore further reducing the process non-uniformity. Packaging materials with selected properties could enhance the process uniformity due to their role as an insulation layer for food products. The results of this research are expected to aid food processors in developing their HPHT processed foods, so the safety of these products can be assured.M.S.Includes bibliographical referencesby Li Zhan