18D-21

J. AHN, Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Rd, 110 Parker Food Science Bldg., Columbus, OH 43210-1007 and V. M. Balasubramaniam.

High-pressure processing has received much attention due to the fact that it can effectively inactivate vegetative cells and extend shelf life with minimized thermal impacts on major attributes of a food product. However, high-pressure alone is not efficient in inactivating bacterial spores. Therefore, pressure assisted thermal processing is of great interest in ensuring microbiological safety of foods. The objective of this study was to investigate the effect of pressure assisted thermal processing on the inactivation of natural spores present in foods. Pressure-thermal resistant spores were screened from red pepper, black pepper, and garlic powder. The samples were subjected to high-pressure (700 MPa) at 105^oC for 3 min. The treatments were plated on trypticase soy agar and incubated aerobically and anaerobically at 37^o C at 24 h. The highly pressure-thermal resistant strain identified as Bacillus sp. was used as the challenge bacterial spores. The natural spores were harvested by centrifugation (8,000×g for 20 min) and diluted to approximately 1.5 × 10⁸ CFU/mL in sterile deionized water. Inactivation experiments were performed at pressures ranging from 0.1 to 700 MPa in combination with different temperatures of 90 and 105^oC for 5 min. The reduction of natural spores increased with increasing pressure and temperature. Spore populations were reduced by 5.16 and 6.01 log₁₀ CFU/mL at 500 and 700 MPa for 5 min at 105^oC, respectively, whereas thermal treatment alone did not significantly reduce the numbers of natural spores. D₁₀₅ values were about 23.49, 2.01, 0.62, and 0.32 at 0.1, 300, 500, and 700 MPa, respectively. Modified Gompertz, nth-order kinetic, and Weibull models fitted well to the survival curves at lower pressures (300 and 500 MPa) and temperature (90^oC), while the log-logistic model (A_f=1.004) produced a better fit at higher pressure (700 MPa). These results provide practical information regarding the pressure-thermal inactivation of natural spores.

Session 18D, Food Microbiology: General
2:00 PM - 5:30 PM, Sunday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana