Pressure-ohmic-thermal sterilization: A feasible approach for the inactivation of Bacillus amyloliquefaciens and Geobacillus stearothermophilus spores

The efficacy of a pressure-ohmic-thermal sterilization (POTS) for Bacillus amyloliquefaciens and Geobacillus stearothermophilus spore inactivation was investigated. Spores (2.5 × 10⁸ cfu/ml) were inoculated in 0.1% NaCl solution (pH 5.0 and 7.0), green pea puree (pH 6.1), carrot puree (pH 5.0) or tomato juice (pH 4.1). Samples were ohmically (50 V/cm) treated at 600 MPa and 105 C for various holding times using a laboratory-scale high-pressure processor. B. amyloliquefaciens and G. stearothermophilus spores suspended in 0.1% NaCl solution (pH 7.0) were inactivated by 4.6 and 5.6 log, respectively, for a 30-min holding time. B. amyloliquefaciens and G. stearothermophilus spores in tomato juice were reduced by 3.1 and 4.8 log, respectively, for a 10-min holding time. Spore germination was highest in the G. stearothermophilus suspended in 0.1% NaCl solution (pH 7.0). POTS treatment appears to be a potent method for inactivating pressure-thermal resistant bacterial spores. Industrial Relevance Food industry is interested in developing superior quality low-acid shelf-stable foods. This study evaluated the pressure-ohmic-thermal sterilization (POTS) for the inactivation of Bacillus amyloliquefaciens and Bacillus stearothermophilus endospores. The impact of food matrices and acidity on the spore resistance was also investigated. Knowledge gained from the study will help the food processors for understanding the importance of various POTS treatment parameters for sterilization of low-acid foods.