P1-71 Thermal Inactivation of Escherichia coli O104:H4 in Ground Beef Supplemented with Citral

Monday, August 1, 2016
America's Center - St. Louis
Vijay Juneja, U.S. Department of Agriculture-ARS, Wyndmoor, PA
Fred Breidt, U.S. Department of Agriculture-ARS, Raleigh, NC
Timothy Mohr, U.S. Department of Agriculture-OPHS, Keizer, OR
Introduction: Use of heat to kill bacteria is the most effective intervention strategy to ensure microbiological safety of thermally processed foods.  Pathogens may survive in undercooked products and can result in food poisoning outbreaks. 

Purpose: We investigated the heat resistance of a three-strain mixture of E. coli O104:H4 in raw ground beef with added citral (0 to 3%, wt/wt). 

Methods: Inoculated meat was packaged in sterile bags and were completely immersed in a circulating water bath stabilized at 55, 57.5, 60 or 62.5°C for a predetermined period of time.  The surviving cell population was enumerated by surface plating meat samples on tryptic soy agar with added 0.6% yeast extract and 1% pyruvate.  Survival equations (log-linear and non-log-linear Weibull models) were fitted to the experimental data.

Results: The Weibull model consistently offered more accurate fit to all survivor curves; root mean square error of the log-linear model was 0.63 versus 0.38 for the Weibull model.  Using the linear model, time to 4-log reduction were 165.0, 86.2, 14.7 and 3.5 min at 55, 57.5, 60 and 62.5°C, respectively; the corresponding times using Weibull model ranged from 164.8 at 55°C to 3.2 min at 62.5°C.  Supplementing ground beef with 1 to 3% citral rendered the pathogen more sensitive to the lethal effect of heat. 

Significance: The results provide food industry with an option to supplement 1 to 3% citral in ground beef and design reduced time and temperature for cooking, that ensures adequate degree of protection against E. coli O104:H4 and at the same time, provide energy conservation and quality products.