To evaluate (1) the efficacy of the optimized GrovacTM system against Salmonella spp. and E.
coli O157:H7 in laboratory-based inoculation studies, and (2) quantify the shelf-life effects of
the Grovacï¿½ system in a retail production and display study at a Costco Wholesale
Findings: Study 1. GrovacTM Inoculation Study <br/>
The retail beef industry has very few options available to choose from in the way of intervention strategies. Over the past ten years, retailers have vigorously pursued consumer education and outsourcing of ground beef production as methods to reduce the risk of E. coli O157:H7 contamination in beef. The GrovacTM system may be a viable method for retailers to use in in-house beef grinding operations. In order to validate the efficacy of this microbial intervention method, beef trim was inoculated with both Salmonella spp. and E. coli O157:H7 and then treated with the GrovacTM system. A water only treatment was run as control in order to provide a process control. <P>
In all four replicate batches inoculated with Salmonella, a reduction in bacterial loads was seen with both the water treatment and the GrovacTM treatment. The samples that were taken from both treatments showed an increase in bacterial reductions when allowed to drain overnight. In fact, in most cases, the amount of bacterial reduction almost doubled. When comparing the GrovacTM treatment to the water only treatment, there was no difference in average recovered populations after 1 h drain. However the GrovacTM treatment had a slightly higher bacterial reduction than the water only treatment after an overnight drain. Total reduction of Salmonella spp. ranged from 0.3 to 0.7 for the water only and 0.4 to 0.9 logs for the GrovacTM after the 1 h and overnight drain, respectively.<P>
A total of 5 replicates were run on E. coli O157:H7 inoculated beef trimmings. In the first replicate, no bacterial reductions were seen for either the water treatment or the GrovacTM treatment. All four of the other replicates had bacterial reductions. For this reason, the first replicate was not considered in the analysis. As previously shown with the Salmonella inoculated beef, the GrovacTM treatment showed slightly higher bacterial reductions when compared to the water treatment only after the overnight drain. Total reductions of E. coli O157:H7 ranged 0.4 to 0.8 logs for the water only and 0.4 to 1.1 logs for the GrovacTM after the 1 h and overnight drain, respectively.<P>
The GrovacTM system is an appropriate microbial intervention to be used at this level of the food chain, adding yet another hurdle to the multiple hurdles already in place in the production of beef.
<P> Study 2. Shelf Life Analysis <br/>
Generic microbiological analysis showed that the GrovacTM treated ground beef had lower aerobic plate counts and E. coli counts than the non-treated ground beef over the three-day test. Fat, moisture, and pH analysis was similar for the non-treated and the 1 hour drain and 18 hour drain treated ground beef samples. Sensory analysis showed no difference between the GrovacTM treated product and the non-treated product.