Viability of Shiga Toxin-producing Escherichia coli, Salmonella, and Listeria monocytogenes within plant burgers and beef burgers during cold storage and following pan frying

Authors: Luchansky, John; Shoyer, Brad; Jung, Yang Jin; Shane, Laura; Osorio, Manuela; Porto-Fett, Anna

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2019
Publication Date: 2/13/2020
Citation: Luchansky, J.B., Shoyer, B.A., Jung, Y.N., Shane, L.E., Osoria, M., Porto Fett, A.C. 2020. Viability of Shiga Toxin-producing Escherichia coli, Salmonella, and Listeria monocytogenes within plant burgers and beef burgers during cold storage and following pan frying. Journal of Food Protection. 83(3):434-442.
DOI: https://doi.org/10.4315/0362-028X.JFP-19-449

Interpretive Summary: Over the past 5 years there has been a spike in the development and consumption of “simulated meats”, namely plant-based burgers and cultured meat, as alternatives to so-called “farm-grown meats”. Information is available on the formulation, nutritional and health benefits, and sensory and quality attributes of several plant-based foods, including plant-based burgers; however, information is lacking on the safety of such foods as it relates to the potential behavior and persistence of three of the top food borne pathogens, namely Shiga toxin-producing Escherichia coli (STEC) , Salmonella spp., and Listeria monocytogenes, during storage and preparation. Thus, we monitored the fate of these three pathogens within inoculated plant-based and beef-based burgers following cooking in a saute pan and after storage for up to 3 weeks. Levels of both Salmonella and STEC decreased slightly when stored at 4degC, whereas during storage at 21degC, pathogen levels increased in beef but decreased in plant burgers. For L. monocytogenes, growth was observed in both plant and beef burgers during storage at 21degC and in plant burgers when stored at 4degC; this pathogen did not grow in beef burgers stored at 4degC. Regarding cooking, reductions of 3.5 to 6.6, 4.8 to 6.9 and 4.4 to 7.0 were observed for Salmonella, STEC, and L. monocytogenes following cooking to 62.8degreeC, 68.3degreeC, or 73.9degreeC, respectively. The observed lethality validates that proper cooking (and handling) would be effective for controlling these three pathogens if present in such products on occasion and in low levels. Since all three pathogens responded similarly to heat in plant-based as in beef-based burgers, well-established cooking parameters required to eliminate STEC, Salmonella, or L. monocytogenes from ground beef should be as effective for controlling cells of these same pathogens in burgers made from a plant-sourced protein.

Technical Abstract: We evaluated the viability of Shiga toxin-producing Escherichia coli (STEC), Salmonella spp., and Listeria monocytogenes cells within plant- and beef-based burgers during storage and cooking. Regarding storage, STEC and Salmonella spp. did not grow (=0.4 log decrease) in either type of burger when stored at 4degC, but increased ca. 2.4 and 0.8 log CFU/g, respectively, in plant but not beef samples (=1.2 log decrease) after 21 days at 10degC. For L. monocytogenes, pathogen levels increased by ca. 1.3 and 2.6 log CFU/g in plant burgers after 21 days at 4 and 10degC, respectively, whereas pathogen levels decreased appreciably (=0.9 log decrease) in beef burgers during storage at 4 or 10degC. Regarding cooking, burgers (ca. 114 g each) formed from plant- and beef-based proteins were inoculated with ca. 7.0 log CFU/g of STEC, Salmonella spp., or L. monocytogenes and cooked in a saute pan. Cooking plant-based or beef-based burgers to 62.8degC, 68.3degC, or 73.9degC delivered reductions ranging from 4.8 to 6.9 log CFU/g for STEC, ca. 4.4 to 7.0 log CFU/g for L. monocytogenes, and ca. 3.5 to 6.6 log CFU/g for Salmonella spp. In general, no significant (P = 0.05) differences in lethality were observed among pathogens or between plant-based and beef-based burgers for burgers cooked to 73.9degC; however, greater (P = 0.05) reductions for all three pathogens were observed in plant-based burgers cooked to 62.8 or 68.3degC when compared to beef burgers. Since all three pathogens responded similarly to heat in plant-based as in beef-based burgers, well-established cooking parameters required to eliminate STEC, Salmonella, or L. monocytogenes from ground beef should be as effective for controlling cells of these same pathogens in burgers made from a plant-sourced protein.