Pressure assisted thermal sterilization

High pressure processing (HPP) can inactivate various types of microorganisms in their vegetative form. However, spores can be resistant to pressures as high as 1000 MPa, which in the absence of heat limits the application of HPP to pasteurization only. A new technology has been recently developed to generate mild pressure by heating the treated liquid food in enclosure. This technology was examined for its ability to inactivate spore forming bacteria (Bacillus cereus and Geobacillus stearothermophilus) to produce a sterile product which retained its original organoleptic characteristics. Results shows that this pressure assisted thermal sterilization process could decrease the decimal reduction time (D-value) and hence, reduce the sterilization temperature significantly. The mild pressure generated assisted spores to germinate allowing the heat to inactivate the germinated spores. Vegetative microorganisms (Saccharomyces cerevisiae and Escherichia coli) were also tested using the technology. However, the effect of this mild pressure on the inactivation was found insignificant.