54F-11

S. RAJAN, V. M. Balasubramaniam, S. Pandrangi, and A. E. Yousef. Dept. of Food Science and Technology, Ohio State Univ., 2015 Fyffe Ct., 110 Parker Food Science Bldg., Columbus, OH 43210-1007

Use of Pressure-Assisted Thermal Processing (PATP) to inactivate bacterial spores in shelf-stable low-acid foods without diminishing product quality has received widespread industry interest. The objective of the study was to compare the efficacy of PATP and thermal processing against Bacillus stearothermophilus spores, inoculated in egg patties or suspended in deionized water. Experiments consisted of inoculating B. stearothermophilus ATCC 7953 spores (10⁸ spores/mL) in egg patties or deionized water and packaging the product in sterile pouches by heat sealing. The sample bags were then placed inside a larger high-barrier plastic pouch and vacuum packaged. Test samples were preheated and PATP treated at 105^o C over various pressure levels (400-700 MPa) and pressure holding times up to 5 minutes using a Quintus model QFP6 high pressure food processor. Thermal inactivation of spores was studied at 121^o C using custom fabricated aluminum tubes; this treatment served as a control. Surviving spores in processed samples were enumerated by plate count agar technique after incubation at 55^o C for 48 hours. Application of PATP accelerated the inactivation of B. stearothermophilus spores in both egg patties and deionized water, compared to the thermal treatment at 121^oC. PATP inactivation progressed rapidly during pressure holding time up to 60s but greater holding times had comparatively limited effect. For the same final process temperature (105^oC), increasing pressure levels from 600 MPa to 700 MPa did not provide additional lethal effects. D-values of B. stearothermophilus in PATP processed egg patties and deionized water were not significantly different. While thermal inactivation of spores followed first- order kinetics, PATP inactivation exhibited non-linear death behavior. Among the models (Modified Gompertz equation, Weibull and Log-logistic equation) tested Weibull model described best PATP inactivation of B. stearothermophilus spores in egg. PATP technology can be used for inactivation of processing-resistant bacterial spores in egg matrix.

Session 54F, Nonthermal Processing: General I
2:00 PM - 5:30 PM, Monday PM Room Hall I-2

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