Sources of Variation at the Retail Level in Bacteriological Condition of Ground Beef ¹

Ground beef from two locker plants using beef trimmings, and two retail stores, using 4.5-kg chub packs of coarse-ground centrally packaged beef as a source of meat, was evaluated microbiologically on the first Monday and Wednesday of every other month for 14 months. Only slight variations in coliform, fecal coliform, coagulase-positive staphylococci, and aerobic plate counts by plant or retail store were noted. Both retail stores using chub packs showed average total aerobic plate counts of 3.5 × 10⁶/g while one locker plant averaged 1.7 × 10⁶/g and the other 7.7 × 10⁶/g. Source of meat for ground beef and holding time of the meat contributed most to differences in microbiological quality. Overall, ground meat packaged on Monday had higher (P<05) average total aerobic plate counts (5.7 × 10⁶/g) than that packaged on Wednesday (2.5 × 10⁶/g) when more recent beef shipments were available. Coliform, fecal coliform, and coagulase-positive staphylococcus counts followed the same patterns as noted for total aerobic plate counts. Total aerobic plate counts in beef increased slightly in the locker plants where game was processed in the fall, in addition to beef. However, game meat did not cause Salmonella contamination of ground beef in plants where both game and beef were processed. Three Salmonella positive samples out of the 112 total ground beef samples and the 112 swabs from used grinders were isolated and serotyped.