ANAEROBIC MICROBIOLOGY OF FRESH BEEF PACKAGED UNDER MODIFIED ATMOSPHERE OR VACUUM

Beef was packaged under CO2 containing < 500 ppm O2 (MAP), vacuum, or air and stored at 0, 2, or 4-degrees-C. Samples were analyzed weekly f or bacterial numbers using anaerobic plate count (pre-reduced medium a nd anaerobic chamber), aerobic plate count, and anaerobic jar plate co unt (MAP samples only) methods. For both MAP and vacuum packaged sampl es, the anaerobic plate count was consistently greater than the aerobi c plate count and for MAP samples the anaerobic plate count was consis tently higher than the anaerobic jar plate count. Differences between plating methods were most frequent during the latter third of 0 and 2- degrees-C storage. Anaerobic isolates from MAP samples were most often lactic acid cocci and staphylococci. No clostridia were isolated from any of the treatments.