Project Summary

A Microbiological Profile of Domestic and Imported Beef Raw Materials Destined for Use in Ground Beef Production

Principle Investigator(s):
J.A. Scanga, G.R. Bellinger, K.E. Belk and G.C. Smith
Colorado State University
Completion Date:
June 1998


Layman’s Summary 

Beef raw materials and final ground beef products were selected from eight commercial grinding facilities in order to determine the effect of contaminants in beef raw materials on final ground beef products. The raw materials selected represented products from fed- beef, culled-beef-cow, culled-dairy-cow and imported beef trimmings. Samples were analyzed for aerobic plate count (APC), total coliform counts (TCC), generic Escherichia coli counts (ECC) and Staphylococcus aureus counts. Combo-bin samples, both core and purge, were tested for the presence or absence of Salmonella spp. and Listeria monocytogenes. Overall, APC counts ranged from 2.0 to 4.5 log CFU/g with the large range being attributed to differing sanitation and hygiene practices of each grinding facility. Samples containing 30% or more fat had higher APC’s than samples with less than 30% fat. This was possibly due to smaller particle size for fatter trimming and the fact that they are handled more during processing. Trimmings from fed-beef had higher APC and TCC counts than culled beef or dairy cow trimmings. 

The overall incidence of pathogens in combo-bin samples was 3.3% and 1.9% for Salmonella spp. and L. monocytogenes, respectively.  Results from purge samples were highly correlated with results from combo-bin samples and overall, purge samples had higher numbers of bacteria than combo-bin samples. Tracking final product back to its raw material source confirmed that a small portion of highly contaminated raw material can adversely affect a much greater quantity of final product. Additionally, the contamination level of beef trimmings increases as the product moves through the grinding process. Therefore, only raw materials known to have acceptable bacterial quality should be used to produce raw ground beef products.