Purpose: The goal of this study was to evaluate the destruction kinetics of group II (nonproteolytic) C. botulinum spores under various HPHT processing conditions.
Methods: Group II C. botulinum spores produced by eight strains from different serotypes (B, E, F) were suspended in ACES buffer (106 spores/ml) and individually processed at 600 MPa, 80°C. To determine the D-value, spore survival was enumerated by plate count on McClung Toabe agar with egg yolk and the plates were incubated anaerobically for seven days at 25°C. Spores exhibiting the highest resistance were further processed at 550 and 650 MPa at 80°C. The z-value as a function of pressure was, later, calculated. Each treatment was repeated in triplicates.
Results: Spores from C. botulinum type F strains exhibited the highest D-values (3.2 to 7.3 minutes) upon processing at 600 MPa at 80°C, followed by type B strains (2.4 to 5.8 minutes) and type E strains (2.6 to 2.7 minutes). Strains 610F, KAP-B-8 and E Russ showed the highest resistance within their respective type and were selected for subsequent experiments. The D-values of these three strains increased at 550 MPa (7.4 to 36.2 minutes) and decreased at 650 MPa (2.0 to 6.0 minutes). Based on the z-value, strains KAP-B-8 and 610F produced spores which were the most resistant to HPHT (128.2°C and 153.8°C, respectively), while spores from E Russ were the least resistant (200.0°C).
Significance: HPHT is an effective method for destroying C. botulinum spores and could potentially be used as a processing method to achieve commercial sterility while maintaining the quality of food products.