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Five treatments: Control (C), Pre-evisceration Electrical Stimulation (CES: 15 Hz, 700 mA, 500 µs pulse width, 45 s pulse duration), vascular Rinse & Chill® (RC), CES + RC (ESRC), and RC with ES after evisceration (RCES:15 Hz, 600 mA, 1000 µs, 45 s), were applied to 21 lambs each. After being excised from the carcass, muscles were vacuum packaged and aged (Longissimus lumborum, LL, 3 and 22 d postmortem; Semimembranosus, SM, 3 d postmortem). Temperature, pH, purge, cooking loss, color, Warner-Bratzler Shear Force (WBSF), and consumer sensory evaluations were determined. CES and ESRC resulted in the fastest drop in pH below 6 and ESRC had the lowest likelihood of cold shortening. Sensory tenderness in the ESRC LL was greater than C. No differences in WBSF were found among treatments. RC generally produced lamb with higher lightness (L*). The rapid drop in pH likely was responsible for the increased purge and cooking loss observed. Color was affected by the order of ES and RC application.

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To control the growth of Clostridium perfringens in cured meat products, the meat and poultry industries commonly follow stabilization parameters outlined in Appendix B, "Compliance Guidelines for Cooling Heat-Treated Meat and Poultry Products (Stabilization)" ( U.S. Department of Agriculture, Food Safety and Inspection Service [USDA-FSIS], 1999 ) to achieve cooling (54.4 to 4.4°C) within 15 h after cooking. In this study, extended cooling times and their impact on C. perfringens growth were examined. Phase 1 experiments consisted of cured ham with 200 mg/kg ingoing sodium nitrite and 547 mg/kg sodium erythorbate following five bilinear cooling profiles: a control (following Appendix B guidelines: stage A cooling [54.4 to 26.7°C] for 5 h, stage B cooling [26.7 to 4.4°C] for 10 h), extended stage A cooling for 7.5 or 10 h, and extended stage B cooling for 12.5 or 15 h. A positive growth control with 0 mg/kg nitrite added (uncured) was also included. No growth was observed in any treatment samples except the uncured control (4.31-log increase within 5 h; stage A). Phase 2 and 3 experiments were designed to investigate the effects of various nitrite and erythorbate concentrations and followed a 10-h stage A and 15-h stage B bilinear cooling profile. Phase 2 examined the effects of nitrite concentrations of 0, 50, 75, 100, 150, and 200 mg/kg at a constant concentration of erythorbate (547 mg/kg). Results revealed changes in C. perfringens populations for each treatment of 6.75, 3.59, 2.43, -0.38, -0.48, and -0.50 log CFU/g, respectively. Phase 3 examined the effects of various nitrite and erythorbate concentrations at 100 mg/kg nitrite with 0 mg/kg erythorbate, 100 with 250, 100 with 375, 100 with 547, 150 with 250, and 200 with 250, respectively. The changes in C. perfringens populations for each treatment were 4.99, 2.87, 2.50, 1.47, 0.89, and -0.60 log CFU/g, respectively. Variability in C. perfringens growth for the 100 mg/kg nitrite with 547 mg/kg erythorbate treatment was observed between phases 2 and 3 and may have been due to variations in treatment pH and NaCl concentrations. This study revealed the importance of nitrite and erythorbate for preventing growth of C. perfringens during a much longer (25 h) cooling period than currently specified in the USDA-FSIS Appendix B.

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Interest in natural/organic meat products has resulted in the need to validate the effectiveness of clean label antimicrobials to increase safety and shelf life of these products. A Response Surface Methodology (RSM) was used to investigate the effects of varying levels of moisture, pH, and a commercial "clean-label" antimicrobial (cultured sugar-vinegar blend; CSVB) on the growth rate of Listeria monocytogenes and Leuconostoc mesenteroides in uncured turkey stored at 4 °C for 16 wk. Twenty treatment combinations of moisture (60% to 80%), pH (5.8 to 6.4), and CSVB (2.5% to 5.0%) were evaluated during phase I to develop growth curves for both microbe types, whereas the interactive effects of pH (5.8 to 6.4) and CSVB (0.0 to 4.75) were tested in 16 treatment combinations during Phase II at a single moisture level using L. monocytogenes only. CSVB inhibited L. monocytogenes growth in 14 of the 20 treatments tested in Phase I and in 12 of the 16 treatments in Phase II through 16 and 8 wk, respectively. In contrast, CSVB had little effect on L. mesenteroides, with growth inhibited in only 4 of 20 treatments in Phase I and was therefore not tested further in Phase II. Significant interactions of the RSM design coefficients yielded a predictive model for L. mesenteroides growth rate, but due to lack of growth, no growth rate model was developed for L. monocytogenes. CSVB was found to be an effective antilisteral antimicrobial, while having little effect on a spoilage microorganism.

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Sodium nitrite has been identified as a key antimicrobial ingredient to control pathogens in ready-to-eat (RTE) meat and poultry products, including Listeria monocytogenes. This study was designed to more clearly elucidate the relationship between chemical factors (ingoing nitrite, ascorbate, and residual nitrite) and L. monocytogenes growth in RTE meats. Treatments of cooked, cured pork sausage (65% moisture, 1.8% salt, pH 6.6, and water activity 0.98) were based on response surface methodology with ingoing nitrite and ascorbate concentrations as the two main factors. Concentrations of nitrite and ascorbate, including star points, ranged from 0 to 352 and 0 to 643 ppm, respectively. At one of two time points after manufacturing (days 0 and 28), half of each treatment was surface inoculated to target 3 log CFU/g of a five-strain L. monocytogenes cocktail, vacuum packaged, and stored at 7°C for up to 4 weeks. Growth of L. monocytogenes was measured twice per week, and enumerations were used to estimate lag time and growth rates for each treatment. Residual nitrite concentrations were measured on days 0, 4, 7, 14, 21, and 28, and nitrite depletion rate was estimated by using first-order kinetics. The response surface methodology was used to model L. monocytogenes lag time and growth rate based on ingoing nitrite, ascorbate, and the residual nitrite remaining at the point of inoculation. Modeling results showed that lag time was impacted by residual nitrite concentration remaining at inoculation, as well as the squared term of ingoing nitrite, whereas growth rate was affected by ingoing nitrite concentration but not by the remaining residual nitrite at the point of inoculation. Residual nitrite depletion rate was dependent upon ingoing nitrite concentration and was only slightly affected by ascorbate concentration. This study confirmed that ingoing nitrite concentration influences L. monocytogenes growth in RTE products, yet residual nitrite concentration contributes to the antimicrobial impact of nitrite as well.

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Thirty red deer ( Cervus elaphus ) stags were slaughtered at three deer slaughter premises (plants A, B, and C) to determine the effects of initial microbial flora on the quality of chilled venison loins stored using three packaging methods: vacuum packaging (VP), modified atmosphere packaging using an ultra-high barrier outer barrier film (CO2-UHB), and modified atmosphere packaging using a dual aluminized polyethylene outer barrier film (CO2-MPET), all of which were stored for 6, 12, and 18 weeks at -1 ± 3°C. Carcasses slaughtered in plant B had higher aerobic plate counts than those killed at either plants A or C. Location of slaughter had little effect on loin quality except for drip loss, pH and anaerobic and lactic acid bacteria counts. Oxygen levels increased in the modified atmosphere packages (P<0.05) during storage from 12 to 18 weeks (CO2-UHB, 1%; CO2-MPET, 0.05%). Loins packaged in CO2 -UHB exhibited less acceptable surface color than meat packaged in CO2 -MPET or VP. Aroma, flavor, texture, and acceptability scores decreased (P<0.05) when loins were stored over 12 weeks regardless of packaging method. pH values of loins packaged in modified atmosphere packs were lower (P<0.05) than those in VP. The regression relationship between percent drip loss and pH was given by % drip = 39.1-6.49 [Standard error (SE) 1.52] pH. Acceptable display color of steaks cut from the loins, regardless of treatment, decreased as loins were stored from 6 to 18 weeks. These results suggest that vacuum packaged venison loins resulted in meat of acceptable quality after 12 and 18 weeks of chilled storage, and that modified atmosphere packaging contributed no additional benefit.