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.