Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/29/2008
Publication Date: 4/1/2009
Citation: Juneja, V.K., Bari, M.L., Inatsu, S., Kawamoto, S., Friedman, M. 2009. Thermal Destruction of Escherichia coli O157:H7 in Sous-vide Cooked Ground Beef as affected by Tea Leaf and Apple Skin Powders. Journal of Food Protection. 72(4):860-865. Interpretive Summary: E. coli O157:H7 is a pathogen of major concern for the food industry since documentation of its association with several outbreaks of foodborne illness. Undercooked meat and meat products are commonly implicated as transmission vehicles in these outbreaks. This emphasizes the need to better define and quantify the heat treatment given to these foods to provide an adequate degree of protection against survival of E. coli O157:H7. We determined that a heat treatment at 57.5 degrees celsius for 132 minutes would kill more than one million bacteria in beef. The heating time can be reduced 3 fold if beef is supplemented with 3 percent apple skin extract. We developed a mathematical model for predicting the destruction of this pathogen in beef. The model can be used to predict the time required at any temperature to kill a certain number of bacteria. This information will be of immediate use to consumers and to the food industry and regulatory agencies to aid in the development of guidelines to ensure safety of the food supply.
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 h to an internal temperature of 55, 58, 60, or 62.5C, and then held for predetermined lengths of time ranging from 210 min at 55C to 10 min at 62.5C. The surviving bacteria were enumerated by spiral plating onto tryptic soy agar overlaid with Sorbitol MacConkey agar. Inactivation kinetics of the pathogen deviated from first order kinetics. D-values (min for the bacteria to decrease by 90%) in the control beef ranged from 67.79 min at 55C to 2.01 min at 62.5C. 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 62.5C. 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.