Thermal death of Escherichia coli O157:H7 in cattle feeds

Abstract

Aims: To determine if the temperatures used in feed manufacture are likely to destroy Escherichia coli O157. Methods and Results: Two commercial feeds were ground and inoculated with E. coli O157 cells. The feeds were heated to 50, 55, 60, 65 or 70°C. Heating produced quadratic survivor curves, with rapid initial decreases. The survival characteristics of E. coli O157 differed in the two feeds. The reductions observed in one feed may not have been due to heat alone. There was evidence that indigenous anti‐E. coli O157 factor(s) in one feed acted with the heat and contributed to the observed rates of bacterial death. Heating at 70°C for 20 or 120 s resulted in approx. 1·3 and 2·2 log reductions in E. coli O157 numbers respectively. Lesser reductions were observed at lower temperatures. Conclusions: The time/temperature combinations used in commercial pelleting processes would not effectively kill high numbers of E. coli O157. Significance and Impact of the Study: This is the first study to look at the survival of E. coli O157 strains after heat treatment within concentrated animal feed. The study provides information on the likely risk of E. coli O157 surviving the animal feed manufacturing process.

Optimization of Antimicrobial Combined Effect of Organic Acids and Temperature on Foodborne Salmonella and Escherichia coli in Cattle Feed by Response Surface Methodology

“…Considering a possible synergistic effect between variables, their optimum levels would provide a set of safety values ensuring a feasible treatment to be implemented in the food industry. The time of heat treatment was fixed to 2 min, which has been reported as enough to achieve a significant reduction in the feed microbial population (Matlho et al, 1997;Hutchison et al, 2007).…”

“…Although microbial inactivation in cattle feed has been scarcely investigated, some studies have analyzed bacterial survival either under thermal treatments (Blank et al, 1996;Hutchison et al, 2007) or acidic conditions (Ha et al, 1998;AlNatour and Alshawabkeh, 2005). Nevertheless, some reports suggest that heat treatment alone may be insufficient to eliminate high numbers of microorganisms (Maciorowski et al, 2006;Hutchison et al, 2007) or that under certain circumstances, organic acids can promote microbial growth in feeds (Lynn et al, 1998).…”

“…Retention times of feed mash depend on the formulation and mass of feed, final temperature, and equipment used (Hutchison et al, 2007). Times of heat treatment from < 1 min at 71.1°C (Matlho et al, 1997) to 3.5-4.0 min at 78°C-80°C (Blank et al, 1996) have been reported for decontaminating poultry feed.…”

“…Although heat treatments are usually effective, combinations of time/temperature for commercial feed production can be insufficient to eliminate high numbers of microorganisms (Maciorowski et al, 2006;Hutchison et al, 2007). Since feeds are nonsterile ( Jones and Richardson, 2004) and sensitive to postprocessing recontamination (Maciorowski et al, 2006), usually more than one strategy is used to prevent microbial growth in feedstuffs.…”

“…Among the wide number of decontamination methods available for feedstuffs, heat treatments are one of the most effective. During animal feed manufacturing, heat treatments occur either at conditioning, and/or during the pelleting process (Hutchison et al, 2007).…”