SYNERGISTIC EFFECT OF PRESSURE, TEMPERATURE AND pH ON INACTIVATION OF BACILLUS SUBTILIS SPORES IN BUFFER AND MODEL FOOD SYSTEMS

Abstract

ABSTRACT The combined pressure‐thermal‐pH influence on inactivation of Bacillus subtilis ATCC 6633 spores (1 × 108 cfu/mL initial count) in citrate‐phosphate buffer was studied over a range of pressure (690 and 827 MPa), process temperature (60, 65, 70 and 75C), pH (3, 5 and 7) and pressure‐holding time (up to 10 min) combinations. The influence of food matrix effect on spore inactivation was studied using tomato puree (pH 4.05) and minced crabmeat (pH 7.25) samples. All the experiments were conducted using a pilot‐scale high‐pressure food processor. Increase in process temperature, pressure and pressure‐holding time increased spore inactivation. Further, the substrate pH and the food substrate also had a significant influence on the spore inactivation. The highest inactivation (≥7 log10 units) was obtained when the spores suspended in pH 3 buffer were processed at 827 MPa–75C for 5 min. Adjusting the product formulation by adjusting its pH can be used as an effective tool in enhancing spore lethality during high‐pressure processing.PRACTICAL APPLICATIONSHigh‐pressure processing with or without the addition of heat has been used effectively as commercial food pasteurization method for a variety of value‐added food products. The current study will help further the development of high‐pressure processed high‐acid or acidified food products.