Survival of Salmonella and the surrogate Enterococcus faecium in cooking of moisture enhanced reconstructed comminuted chicken patties by double pan-broiling

Thermal Inactivation of Salmonella Surrogate, Enterococcus faecium, in mash broiler feed pelleted in a university pilot feed mill: Microbiology and Food Safety Section

This study evaluated the thermal inactivation kinetic parameters of a Salmonella surrogate Enterococcus faecium (E. faecium) during feed manufacture in a university pilot feed mill setting. A batch of 227 kg mash broiler feed was pelleted after being inoculated with 1,000 mL of nalidixic acid (NaL) resistant E. faecium (5.4 log10CFU/g) at 70°, 75°, 80°, and 85°C for 0 to 115 s. Bacterial survival cell counts were analyzed by spread plating onto bile esculin agar plus 200 ppm of NaL. Microbial data and thermal kinetic parameters [n=6, Global-Fit and United States Department of Agriculture (USDA)-Integrated-Predictive-Modeling-Program software] were analyzed by R-software (orthogonal polynomial model). Pelleting mash broiler feed at 70°, 75°, 80°, and 85°C decreased (P < 0.05) E. faecium cell counts by 0.81, 1.18, 1.69, and 1.94 log10 CFU/g after 115 s, respectively. D-values of orthogonal polynomial, Linear with Tail, Weibull models for E. faecium at 70°, 75°, 80°, and 85°C were 47.1 to 135.4, 42.1 to 135.2, and 51.4 to 118.8 s, respectively. These results suggest that pelleting at 80 or 85°C reduces E. faecium populations the fastest, and it takes at least 50 s to reduce populations by 1 log10 CFU/g at these temperatures. Thermal inactivation for E. faecium took longer and required higher temperatures in the feed mill than lab estimates, highlighting the importance of testing thermal inactivation temperatures in the field to ensure proper feed hygiene.

Dual-Species Biofilms Formed by Escherichia coli and Salmonella Enhance Chlorine Tolerance

Outbreaks of Escherichia coli and Salmonella in food might be associated with the cross-contamination of biofilms on food-contact surfaces. The knowledge of the sanitization of mono-species biofilm on the food-contact surface is well established, while mixed-species biofilm occurs more naturally, which could profoundly affect the efficacy of sanitizer.

Thermal inactivation of Salmonella Typhimurium and surrogate Enterococcus faecium in mash broiler feed in a laboratory scale circulated thermal bath

This study compares kinetic parameters of Salmonella and surrogate Enterococcus faecium in mash broiler feed during thermal inactivation. Two-gram samples of mash broiler feed were added into a filtered sample bag and inoculated with nalidixic acid (NaL, 200 ppm) resistant S. Typhimurium or Enterococcus faecium, followed by vacuum-packaging and heating in a circulated thermal water bath at 75°, 85°, and 95°C for 0 to 180 s. Counts of bacterial survival were analyzed on tryptic soy agar and bile esculin agar plus 200 ppm of NaL. Microbial data and thermal kinetic parameters (n = 8, Global-Fit and United States Department of Agriculture [USDA]-Integrated-Predictive-Modeling-Program software) were analyzed by JMP software. Heating mash broiler feed at 75°, 85°, and 95°C decreased (P < 0.05) Salmonella cell counts by >6 log₁₀CFU/g after 180, 60, and 50 s, respectively. Heating E. faecium in feed at 75°, 85°, and 95°C for 180, 120, and 70 s achieved reductions of 3, 6, and >6.5 log₁₀CFU/g, respectively. D-values of linear, Weibull models, and z-value of Salmonella at 75°, 85°, and 95°C were 1.8 to 11.2, 4.2 to 21.8, and 28.6 s, respectively, which were lower (P < 0.05) than those of E. faecium (3.7-18.1, 8.5-34.4, and 34.1 s). Linear with Tail, Linear with Tail and Shoulder, and Weibull with tail equations revealed that E. faecium were more resistant (P < 0.05) to heat than Salmonella as shown by longer "Shoulder-time" (26.5 vs. 16.2 s) and greater "Tail" effect (4.4-4.5 vs. 2.5-2.6 log₁₀CFU/g). Results clearly suggested that E. faecium can be used as a surrogate for Salmonella to validate thermal inactivation during feed manufacture.