55-5 |
R-Phycoerythrin as a time-temperature integrator in beef patties |
S. E. SMITH1, A. Orta-Ramirez, J. F. Steffe, R. Y. Ofoli, and D. M. Smith. (1) Dept. of Food Science & Human Nutrition, Michigan State Univ., 3340 Anthony Hall, East Lansing, MI 48824-1224 Inadequate cooking of beef patties is a common cause of food borne disease outbreaks. A 5.0 log reduction in Salmonella has been proposed as the USDA lethality performance standard for fully cooked meat patties to supplement safe harbor cooking requirements. Previous work has shown that fluorescence decay of the algal protein, R-phycoerythrin (PE), can be used to distinguish between different thermal processes in a model system. The objective of this study was to relate PE fluorescence decay to the inactivation of Salmonella in beef patties cooked using adequate and inadequate thermal processes as defined by the USDA safe harbor requirements and proposed lethality standards. Ground beef containing 4.8 or 19.1% fat was inoculated with an 8-strain cocktail of Salmonella to 108 CFU/g and formed into 113g patties. Capillary tubes containing PE in borate buffer, pH 9.0, were attached to a thermocouple and inserted horizontally into the patties. Patties (n=43) were cooked on a 177°C grill for 6-13 min to reach internal temperatures ranging from 57 to 77°C. Patties were analyzed for Salmonella survivors and the fluorescence decay of PE was determined. Thermal lethality of each process was calculated at a reference temperature of 65°C. Twenty-four of 43 high fat patties met the USDA safe harbor regulations and had thermal lethalities greater than 66s, whereas only 20 of these patties met the 5 log lethality standard. Only 1 of 20 low fat patties meeting USDA regulations did not meet the proposed lethality standard. A normalized PE fluorescence value of 0.3 (CI=99%) indicated that patties had been processed sufficiently to reduce Salmonella by 5 log cycles. PE has potential for use as a marker to verify processing adequacy when Salmonella cannot be used in a plant due to safety concerns.
Session 55, Muscle Foods: Fresh Meat Quality
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