Project Summary

Efficacy of the Grovac™system for Decontamination of Retail Beef Trimmings: Process Validation Against Pathogens and Commercial Shelf-Life Study

Principle Investigator(s):
Robin Forgey, Randall K. Phebus, Thomas Herald, and James Marsden
Kansas State University
Completion Date:
May 2004



Since 1986, ground beef manufacturers, retailers, food service and consumers have had to deal with the risk of E. coli O157:H7 in their ground beef. The USDA and the ground beef industry have spent several years and millions of dollars working to combat this issue through the development of antimicrobial intervention strategies, the introduction of HACCP systems, and consumer education programs. Most of these risk reduction efforts have been aimed at the beef manufacturing plants, particularly slaughter level carcass decontamination systems, with a good degree of success. However, to best ensure the microbial safety of retail ready ground beef, sequential intervention technologies (hurdles) throughout the production chain need to be developed and implemented. While cooking beef to 160 °F will eliminate the hazard of E. coli O157:H7 from the product, it does not eliminate the problems associated with cross-contamination that often occur in consumers’ kitchens or food service operations.

Commercial ground beef is produced by mixing pieces of beef trimmings from larger beef cuts (subprimals) during fabrication processes and grinding fat and lean component streams into coarsely or finely ground wholesale products. The percent fat for each grind is obtained by mixing the proper combination of lean muscle meat with fat from trimmings. Thus, a production load of ground beef can contain meat from many different cuts of beef from varying sources and of differing quality. The manufacture of this product in centralized beef processing facilities ensures production under strict standards of hygiene and quality control. The retail butcher’s shop faces many challenges in today’s marketplace. They have the pressures of increased competition, a shortage of skilled meat cutters and the risk associated with selling ground beef that may harbor E. coli O157:H7. At the retail store (butcher shop) level, the production of ground beef allows minimization of economic (yield) losses associated with trimming steaks and roasts. These table trimmings are generally mixed with coarse ground chubs for final grinding, followed by retail case display for 1-2 days. Until now, there has been no antimicrobial intervention strategy available to the retail meat grinder that would allow him to minimize his risk of selling contaminated beef. This void in retail-level technology puts the entire beef production complex at risk of USDA action, recalls, negative publicity, and litigation in the event contamination occurs, especially if it affects public health. By placing a validated intervention technology at this final ground beef production stage, where contamination with enteric pathogens would be expected to be infrequent and at very low levels, a significant hurdle would be in place to further reduce the likelihood that pathogen contaminated ground beef would reach the consumer.

The Grovac™ Intervention System is a simple and inexpensive method designed to lower bacterial levels on ground beef while extending the shelf life of the product. The Grovac™ system is designed to be used in a batch process and is adaptable to small volume situations often encountered in retail butcher shop operations. It involves treating the beef trimmings in a mixture of citric acid and a hypotonic salt solution while tumbling under vacuum. The citric acid lowers the pH on the outside of the beef to a level where the bacteria can no longer survive and acts as an antioxidant in the final product, delaying the conversion of oxymyoglobin to metmyoglobin, which stabilizes the bright red color for a longer period of time.

The Grovac™ system has been commercially tested and is now in use in fresh seafood and poultry processing facilities. At Kansas State University, this system was evaluated against meat-borne pathogens inoculated onto beef trimmings with encouraging results. Reductions on acid-adapted pathogens were slightly less than 1 Log CFU/g and total aerobic bacterial reductions were 1.7 Log CFU/g (Touvet, 2002). Since these studies, in-house studies at Costco Wholesale have led to an adjustment (optimization) in processing parameters of the beef trimmings in the GrovacTM system. In these Costco studies, generic microbial reductions have remained good and the shelf-life stability (color) of retail ground beef has been enhanced.

The stated objectives for this work were 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 Grovac™ system in a retail production and display study at a Costco Wholesale warehouse. 

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