Inactivation of Escherichia coli O157:H7 during cooking of non-intact beef treated with tenderization/marination and flavoring ingredients

Bactericidal effect of marinades on meats against different pathogens: a review

Marinades are seasoned liquids used to improve tenderness, palatability, flavor, color and/or texture of different meats. In addition to contribute to the sensory characteristics, marinates can inactivate food microorganism as well. The purpose of this study was to assess the current state of knowledge regarding the effect of marinades on meats and important food pathogens. Using a systematic review of literature, different types of marinades were evaluated, identifying its ingredients, concentrations, temperature, marinating time and their effect on Salmonella, Escherichia coli, Listeria monocytogenes, Campylobacter and Vibrio. Findings demonstrated that the use of marinades on meats not only prevents the growth of pathogens but also inactivates food pathogens. Most marinades were able to reduce < 3 log CFU/g of pathogens, and Vibrio populations demonstrated the highest reductions (> 4 log CFU/g). The pH was the most pronounced parameter influencing the pathogens inactivation, however, ingredients and storage temperature also affected pathogen reduction in marinades.

A Comparison Study of Quality Attributes of Ground Beef and Veal Patties and Thermal Inactivation of Escherichia coli O157:H7 after Double Pan-Broiling Under Dynamic Conditions

This study compared the quality variation and thermal inactivation of Escherichia coli O157:H7 in non-intact beef and veal. Coarse ground beef and veal patties (2.1 cm thick, 12.4 cm diameter, 180 g) inoculated with E. coli O157:H7, aerobically stored before double pan-broiling for 0-360 s without rest or to 55, 62.5, 71.1, and 76 °C (internal temperature) with 0.5- or 3.5-min rest. Microbial population and qualities including color, cooking losses, pH, water activity, fat, and moisture content, were tested. After cooking the beef and veal patties, the weight losses were 17.83-29%, the pH increased from 5.53-5.60 to 5.74-6.09, the moisture content decreased from 70.53-76.02% to 62.60-67.07%, and the fat content increased (p < 0.05) from 2.19-6.46% to 2.92-9.45%. Cooking beef and veal samples with increasing internal temperatures decreased a* and b* values and increased the L* value. Escherichia coli O157:H7 was more sensitive to heat in veal compared to beef with shorter D-value and "shoulder" time. Cooking to 71.1 and 76 °C reduced E. coli O157:H7 by >6 log CFU/g regardless of rest time. Cooking to 55 °C and 62.5 °C with a 3.5-min rest achieved an additional 1-3 log CFU/g reduction compared to the 0.5-min rest. Results should be useful for developing risk assessment of non-intact beef and veal products.

Comparative Effect of Heat Shock on Survival of O157:H7 and Non-O157 Shiga Toxigenic Escherichia coli and Salmonella in Lean Beef with or without Moisture-Enhancing Ingredients

Thermal tolerance of pathogenic bacteria has been shown to increase after exposure to sublethal elevated temperatures, or heat shock. We evaluated the effect of heat shock at 48°C on thermal tolerance (D_55°C) of cocktails of O157 and non-O157 Shiga toxigenic Escherichia coli (STEC) and Salmonella in lean ground beef with or without moisture-enhancing ingredients. Beef was moisture enhanced to 110% (w) with a 5% NaCl-2.5% sodium tripolyphosphate (w/w) brine. Meat, with or without added brine, was inoculated (∼10⁸ CFU/g) and heat shocked at 48°C for 0, 5, or 30 min, followed by isothermal heating at 55°C. Inoculated control samples were unenhanced and were not subject to heat shock. From the linear portion of the log CFU per gram surviving cells over time plots, D_55°C-values (minutes) were calculated. D_55°C was 20.43, 28.78, and 21.15 min for O157, non-O157, and Salmonella controls, respectively. Overall, heat shock significantly increased D_55°C, regardless of pathogen (P < 0.05). After 30 min of heat shock, D_55°C increased 89 and 160% for O157 STEC, 32 and 49% for non-O157 STEC, and 29 and 57% for Salmonella, in unenhanced and enhanced samples, respectively, relative to the pathogen control. D_55°C for Salmonella was the same or significantly less than for O157 and non-O157 STEC, regardless of heat shock, and was significantly less than for O157 and non-O157 STEC in all trials with moisture-enhanced meat (P < 0.05). Moisture-enhancing ingredients significantly increased D_55°C, regardless of pathogen (P < 0.05). We suggest that thermal processes validated against Salmonella may not prove effective against STEC in all cases and that regulators of the beef industry should focus attention on STEC in nonintact moisture-enhanced beef products.