Fate of Shiga toxin-producing Escherichia coli in meat bars during processing and storage: a consumers' perspective

Authors: Luchansky, John; MAYHEW, MELANIE - Delaware Valley College; Jung, Yang Jin; KLINEDINST, AMY - Delaware Valley College; HARKINS, LAUREN - Former ARS Employee; Shane, Laura; Osorio, Manuela; MCGEARY, LIANNA - Queen'S University - Ireland; TRAUGHER, ZACHARY - Former ARS Employee; Shoyer, Brad; CHAPMAN, BEN - North Carolina State University; COPE, SARAH - North Carolina State University; CAMPANO, STEPHEN - Hawkins, Inc; Porto-Fett, Anna

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2019
Publication Date: 6/24/2019
Citation: Luchansky, J.B., Mayhew, M., Jung, Y.N., Klinedinst, A., Harkins, L., Shane, L.E., Osoria, M., Mcgeary, L., Traugher, Z., Shoyer, B.A., Chapman, B., Cope, S.J., Campano, S.G., Porto Fett, A.C. 2019. Fate of Shiga toxin-producing Escherichia coli in meat bars during processing and storage: a consumers' perspective. Journal of Food Protection. 82(7):1249-1264. https://doi.org/10.4315/0362-028X.JFP-18-453.
DOI: https://doi.org/10.4315/0362-028X.JFP-18-453

Interpretive Summary: Although jerky remains the dominant meat snack, comprising some 50% of the global market, there has been a ca. 67% increase in sales of meat bars over the past 10 years or so. Although meat bars also contain a lean protein source (e.g., beef, bison, turkey), in contrast to jerky, the other main ingredients are dried fruit (e.g., cranberries), spices (e.g., paprika, black pepper), and nuts (e.g., pecans, sunflower seeds): meat bars also typically contain celery powder (i.e., a natural curing salt) instead of nitrates or other artificial ingredients. Although increasingly popular among consumers, relatively little has been published on the composition, formulation, texture, nutritional aspects, processing conditions, and/or the microbiological profile and overall wholesomeness of meat bars. For these reasons we conducted a nationally-representative online survey and learned that some 70% of 1050 respondents were not familiar with meat bars. We also learned that most respondents preferred beef as the primary protein source, with most respondents purchasing the product (507 of 545, 88) rather than making their own meat bars. Of those respondents who made their own meat bars, of the 70% (46 of 66) who measured temperature during cooking/drying, only 27% (18 of 66) reported using a thermometer-like tool to determine doneness. As another component of this study, we made meat bars using a recipe and dehydration conditions found online. We inoculated the batter with about 3 million cells of Shiga toxin-producing E. coli (STEC) per gram and then cooked/dehydrated the inoculated meat bars in a commercial dehydrator set at either 62.8degC (145degF) for 6 h, 71.1degC (160degF) for 4 h, or 62.8degC (145°F) for 2 h and then at 71.1degC (160degF) for 2 h. In short, our findings validated that heating/drying meat bars for 2 to 6 hours at 62.8degF and/or 71.1degC is sufficient for eliminating levels of STEC likely to be encountered in/on the raw materials and ingredients used to prepare meat bars. This study provides valuable information for producers and policy makers to enhance the safety of this expanding line of hand-held, shelf-stable, meat-based, energy/snack products.

Technical Abstract: A nationally-representative online omnibus survey revealed that ca. 70.8% (743 of 1,050) of U.S. citizens are not familiar with meat bars, a hand-held, nutrient-dense, portable energy/snack food containing a lean protein source along with fruit, spices, and/or nuts. A second nationally-representative online survey of some 545 participants specifically recruited based on their familiarity with meat bars established that beef was the preferred protein source, with most respondents purchasing the product (507 of 545, 88%), primarily from grocery stores (53%), rather than making their own meat bars (66 of 545, 12%). Of those respondents who made their own meat bars, the majority (52 of 97, 54%) obtained their recipes online. Of the 70% (46 of 66) who measured temperature during cooking/drying, only 27% (18 of 66) reported using something like a thermometer (e.g., “thermostat”, “temp gauge”, or themoter”) to determine doneness. In Phase II, meat bar batter was prepared with or without encapsulated citric acid (ECA; 0.74%) and ground beef (65%; 90% lean/10% fat), chopped pecans (15%), golden flaxseed flour (9.7%), chopped cranberries (5.0%), chopped sunflower seeds (3.1%), sea salt (1.1%), black pepper (0.8%), and celery powder (0.35%). Next, we inoculated (ca. 6.5 log CFU/g) the batter with an eight-strain, rifampicin-resistant (100 µg/ml) cocktail of Shiga toxin-producing Escherichia coli (STEC), portioned it by hand (40 + 0.1 g each), and then placed it onto trays with rectangular shapes of uniform size. In each of three trials, meat bars were separately cooked/dried, without the addition of humidity, in a commercial, stainless-steel dehydrator set at either 62.8degC (145degF) for 6 h, 71.1degC (160degF) for 4 h, or 62.8degC (145degF) for 2 h and then at 71.1degC (160degF) for 2 h. Regardless of the cooking/drying treatment, inclusion of ECA in the formulation resulted in a pH decrease (ca. pH 5.5 to ca. pH 4.9) in the finished product. In the absence of ECA, when meat bars were cooked/dried at 62.8degC for 6 h, 160degF for 4 h, or 62.8degC for 2 h and then at 71.1degC for 2h, levels of STEC were reduced by 6.2, 6.3, and 5.2 log CFU/g, respectively. When ECA was added to the formulation, pathogen levels decreased by ca. 6.0, 6.6, and 6.0 log CFU/g in meat bars cooked/dried at 62.8°C for 6 h, 71.1degC for 4 h, or 62.8degC for 2 h and then at 71.1degC for 2 h, respectively. Our results validated that a =5.0-log reduction in STEC numbers could be achieved in meat bars formulated with or without ECA for all cooking/drying conditions tested herein. Producers and consumers, as well as regulators, will likely benefit from these scientifically sound findings, especially the nutritional and wholesomeness components of these protein-rich snacks, but also from insights on consumer preferences for purchasing and/or preparing meat bars.