Escherichia coli O157:H7 Survival, and or Potential Introduction on Beef Carcass Surfaces During Initial Chilling and Characterization of Hot Box Best Practices

<p>Findings: A research study, conducted by scientists at Colorado State University for the Cattleman's Beef Board and state beef councils by the National Cattleman's Beef Association and funded by beef and veal producers and importers through their $1-per-head checkoff contribution, found that due to the effectiveness of multiple intervention strategies implemented at most North American beef processing facilities, to reduce bacterial contamination found on carcass surfaces prior to chilling, differences between chilling methods (spray-chilling versus dry-chilling) are nullified. This research also found that differences in bacterial reduction during chilling across plants are dependant upon the rate of carcass surface temperature decline. Aerobic plate count (APC), TCC and ECC populations recovered from carcasses in three commercial processing facilities were inversely proportional to rates of surface temperature decline; with the fastest rate of surface temperature decline to 4o C having the largest reductions in APC, TCC and ECC populations during chilling. Aerobic plate count, TCC and ECC populations were higher in samples recovered from the lower region of hot carcass, when compared to populations recovered from the upper region of the same carcasses. These results are most likely due to a rinsing effect created by spray and/or wash interventions on the harvest floor prior to chilling, carrying bacteria found on the upper region of the carcass surface towards the lower region. </p>
<p>Escherichia coli O157:H7 was found in fat tears created during mechanical hide removal, although all APC, TCC and ECC populations were all below detectable limits (< 2.0 logs 100/cm2). This and other research concluded that intervention strategies are capable of reducing competitive flora on the carcass surface, while merely injuring some pathogenic organisms. These stressed microbes are then rinsed into tears, settling between the outer fat layer and carcass lean. Therefore, it is essential that slaughter interventions are capable of killing rather than stressing pathogenic bacteria. Slaughter floor and hot box good manufacturing procedures (GMP's) practices modified at a commercial processing plant resulted in greater reduction in APC, TCC and ECC populations during carcass chilling. However, reductions in bacterial populations at this plant were still smaller than the bacterial reductions found at the other two facilities evaluated during this research, suggesting other factors may contribute to reductions in APC, TCC and ECC. One such factor could be surface temperature decline as histories were evaluated at all three facilities, and it was noted that plants with the smallest reduction in bacterial populations during chilling, had the slowest rate of carcass surface temperature decline. Results from this study support the effectiveness of multiple intervention strategies to reduce bacterial populations on carcasses both before entering the hot box and following chilling and indicates that current industry practices of spray-chilling carcasses does not adversely affect the prevalence of E. coli O157:H7.</p>