| Abstrakt: |
This study compares kinetic parameters of Salmonellaand the surrogate Enterococcus faeciumin 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 E. 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) Salmonellacell counts by >6 log10CFU/g after 180, 60, and 50 s, respectively. Heating E. faeciumin 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 Salmonellaat 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. faeciumwere more resistant (P< 0.05) to heat than Salmonellaas 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. faeciumcan be used as a surrogate for Salmonellato validate thermal inactivation during feed manufacture. |
