Submitted to: UJNR Food & Agricultural Panel Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/30/2008
Publication Date: 8/25/2008
Citation: Juneja, V.K., Bari, M.L., Inatsu, Y., Kawamoto, S., Friedman, M. 2008. Tea leaf and apple skin powders facilitate thermal destruction of escherichia coli o157:h7 in raw ground beef. UJNR Food & Agricultural Panel Proceedings.
Technical Abstract: We investigated the heat resistance of a four-strain mixture of Escherichia coli O157:H7 in raw ground beef in both the absence and presence of white and green tea powders and an apple skin extract. Inoculated meat, packaged in bags, was completely immersed in a circulating water bath and cooked for 1 hr to an internal temperature of 55, 58, 60, or 62.5 degree C, and then held for predetermined lengths of time ranging from 210 min at 55 degree C to 10 min at 62.5 degree C. The surviving bacteria were enumerated by spiral plating onto tryptic soy agar overlaid with Sorbitol MacConkey agar. Inactivation kinetics of the pathogens deviated from first order kinetics. D-values (minutes for the bacteria to decrease by 90%) in the control beef ranged from 67.79 min at 55 degree C to 2.01 min at 62.5 degree C. D-values determined by a logistic model ranged from 36.22 (D1 = D-value of a major population of surviving cells) and 112.79 (D2 = D-value of a minor subpopulation) at 55 degree C to 1.39 (D1) and 3.00 (D2) at 62.5 degree C. Significant increased (p < 0.05) sensitivity of the bacteria to heat was observed with the addition of 3% added antimicrobials. The apple powder induced 62 to 74% reductions in D-values at the four temperatures, while reductions with added tea powders ranged from 18 to 58% of control values. Thermal death times from this study will assist the retail food industry to design cooking regimes that ensure safety of beef contaminated with E. coli O157:H7. The plant antimicrobials assessed in this study should improve microbial safety and quality of ground beef at lower times and temperatures of heating.