Microbiological conditions of mechanically tenderized beef cuts prepared at four retail stores.

A group of 25 retail cuts of mechanically tenderized beef prepared during usual commercial operations at store facilities were obtained from each of four retail stores. Aerobes, coliforms, Escherichia coli and organisms that formed black or grey colonies on Harlequin agar (HA), a medium formulated for the recovery of Listeria, were enumerated in samples from the surfaces and the deep tissues of cuts. For the four groups of cuts, the mean numbers of aerobes on the surfaces of cuts differed by <1 log unit, but the numbers of aerobes recovered from the deep tissues differed by up to 2 log units. Few coliforms, E. coli or organisms that formed black or grey colonies on HA, which were mostly staphylococci, were recovered from surfaces and very few or none were recovered from deep tissues. Meat from the stores which provided product with the least or most bacteria in the deep tissues were cooked to maximum central temperatures that ranged from >63 to <68 degrees C. Cooking reduced the numbers of aerobes in the deep tissues of most portions to <1 log cfu/10 g. Cooking to a medium rare condition may be adequate for assuring the microbiological safety of mechanically tenderized beef that is prepared without excessive contamination of deep tissues.