Inactivation of Geobacillus stearothermophilus spores in low-acid foods by pressure-assisted thermal processing.

Abstract

The effect of pressure-assisted thermal processing (PATP) on the inactivation of Geobacillus stearothermophilus spores was determined in deionized water, cooked ground beef, egg patty mince, whole milk and mashed potatoes at 105 °C under 500 and 700 MPa. The numbers of G. stearothermophilus spores in deionized water and milk were reduced by more than 6 log CFU mL(-1) at 700 MPa and 105 °C, whereas those in cooked beef were reduced by 4.27 log CFU g(-1). The inactivation patterns of G. stearothermophilus spores in all food matrices followed nonlinear behavior, showing that Weibull model fitted well to the inactivation curves of G. stearothermophilus spores in low-acid foods. The complex food matrices caused a protective effect on the inactivation of G. stearothermophilus spores during PATP. The results provide useful information in inactivation kinetics of bacterial spores for validating PATP-processed low-acid foods.