|BRAR, JAGPINDER - Purdue University|
|WADDELL, JOLENA - Tarleton State University|
|BAILEY, MATTHEW - University Of Georgia|
|CORKRAN, SYDNEY - Purdue University|
|VELASQUEZ, CARMEN - Purdue University|
|SINGH, MANPREET - University Of Georgia|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2017
Publication Date: 5/14/2018
Citation: Brar, J.S., Waddell, J.N., Bailey, M., Corkran, S., Velasquez, C., Juneja, V.K., Singh, M. 2018. Thermal inactivation of shiga-toxin producing escherichia coli in ground beef with varying fat contect. Journal of Food Protection. 81:986-992. https://doi.org/10.4315/0362-028X.JFP-17-455.
Interpretive Summary: Shiga Toxin Producing Escherichia coli is a pathogen of major concern for the food industry since documentation of its association with several outbreaks of foodborne illness. Undercooked beef is commonly implicated as transmission vehicles in these outbreaks. This emphasizes the need to better define and quantify the heat treatment given to beef to provide an adequate degree of protection against survival of this pathogen. We determined that a heat treatment at 60C for 9.5 min would kill more than one million bacteria in beef. Fat content of beef exhibits protective effect against heat lethality at lower cooking temperatures. 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 cooked beef.
Technical Abstract: Decimal reduction time (D-value) was calculated for six non-O157 Shiga toxin producing Escherichia coli (STEC) in laboratory medium and ground beef. For laboratory medium, overnight grown culture of each strain of STEC was divided into 10 ml sample bags and heated in a water bath for a specific time based on the temperatures. Survival curves were generated by plotting the surviving bacterial population against time and linear-log primary model was used to estimate the D-values from survival curves. z-values were calculated by plotting the log10D-values against temperature. Similarly, for ground beef, six fat contents, 5, 10, 15, 20, 25, and 30% of ground beef were formulated for this study. Inoculated meat was divided into 5-g pouches and submerged in a water bath set at specific temperatures (55, 60, 65, 68, and 71.1C). The average D-value for these strains in laboratory medium was 17.96 min. at 55C, which reduced significantly (p less than 0.05) to 1.58 min. at 60C and then further reduced (p less than 0.05) to 0.46 min. at 65C. In ground beef, a negative co-relation (p less than 0.05) between fat content of ground beef and D-values was observed at 55C. However, at temperatures greater than 60C, there was no impact (p more than 0.05) of fat content of ground beef on the thermal resistance of non-O157 STECs. The data generated from this study can be helpful for the meat industry to develop predictive models for thermal inactivation of non-O157 STECs in ground beef with varying fat contents.