A Comparative Study of the Microbiology of Commercial Vacuum-Packaged and Hanging Beef

The microbiological quality of 150 samples of commercial vacuum-packaged beef knuckles and 150 samples of non-vacuum-packaged hanging beef knuckles were tested. Samples were obtained at random from commissaries at several locations just before distribution of the beef to retail stores. In general, the vacuum-packaged beef had 1 to 2 logs higher indicator bacterial levels than the hanging beef. The odor and appearance of all 300 samples of beef were normal, even though some individual beef samples had rather high bacterial counts. Salmonella was detected in only 1 sample out of all the 300 tested. Yersinia enterocolitica was recovered from 66 samples of vacuum-packaged beef and from only 4 samples of hanging beef. None of the Y. enterocolitica recovered from beef contained the virulence plasmid or were virulent to mice. Most probably these rhamnose-positive and esculin-positive Y. enterocolitica strains recovered from vacuum-packaged beef are not a potential health hazard.