ARS | Publication request: Enhancing the thermal destruction of Escherichia coli O157:H7 in ground beef patties by trans-cinnamaldehyde

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 2010
Publication Date: September 1, 2010
Citation: Amalaradjou, M., Ramanathan, R., Bhaskaran, S., Charles, A., Johny, A., Valipe, S., Mattson, T., Schreiber, D., Mancini, R., Venkitanarayanan, K., Juneja, V.K. 2010. Enhancing the thermal destruction of Escherichia coli O157:H7 in ground beef patties by trans-cinnamaldehyde. Applied and Environmental Microbiology. 27:841-844.

Interpretive Summary: Food poisoning outbreaks due to E. coli O157:H7 have been associated with inadequate cooking of contaminated ground beef in retail food service operations. Therefore, it is important to include an antimicrobial hurdle at the consumers' end to ensure inactivation of a pathogenic bacterium, E. coli O157:H7 in inadvertently undercooked ground beef patties. In this study, the efficacy of trans-cinnamaldehyde (TC), an FDA approved natural antimicrobial in foods, in decreasing the heat resistance of E. coli O157:H7 in ground beef was assessed. We found that a combination of TC and cooking temperature had a greater lethality on E. coli O157:H7 survival in patties than TC or heat alone. These findings will be of immediate use to the retail food service operations and regulatory agencies to ensure the safety of the cooked foods.

Technical Abstract: This study investigated the effect of trans-cinnamaldehyde, an active ingredient in cinnamon, for inactivating E. coli O157:H7 in undercooked ground beef patties. A five-strain mixture of E. coli O157:H7 was inoculated into ground beef (90% lean and 10% fat) at approximately 7.0 log CFU/g, followed by the addition of trans-cinnamaldehyde (0, 0.15, and 0.3%). The contents were mixed, formed into patties and kept at 4C for 5 days or at -18C for 7 days. On each sampling day (0, 1, 3, 5 and 7), patties were cooked to an internal temperature of 60C or 65C, and the population of viable E. coli O157:H7 was determined. Trans-cinnamaldehyde reduced E. coli O157:H7 counts by greater than 5.0 log CFU/g in patties cooked to 60 or 65C (P < 0.05) relative to controls. In the control patties cooked to 65C, trans-cinnamaldehyde reduced the population by a maximum of 3.0 log CFU/g by day 5. Although trans-cinnamaldehyde exerted little antimicrobial activity on E. coli O157:H7 in patties stored at 4 or -18C, the combination of trans-cinnamaldehyde and cooking brought about substantial reductions (P < 0.05) in the pathogen counts. The D-values of E. coli O157:H7 in trans-cinnamaldehyde-treated ground beef patties at 60 and 65C were significantly (P < 0.05) lower than those of the pathogen in control patties. Surface color (a*), lipid oxidation (TBARS), pH, and ratio of 630/580 nm were also measured. Results indicated that trans-cinnamaldehyde containing patties were more color stable (greater a* and ratio of 630/580 nm) and had a lower lipid oxidation (P < 0.05) compared with control samples during storage. Results of this study indicate that trans-cinnamaldehyde enhanced the killing of E. coli O157:H7 in undercooked ground beef patties by increasing its heat sensitivity, and could potentially be used as an antimicrobial additive for ensuring the pathogen inactivation in undercooked patties. Detailed sensory studies are however necessary before recommending the use of trans-cinnamaldehyde in ground beef patties.