GROWTH-SURVIVAL OF NATURAL FLORA AND LISTERIA-MONOCYTOGENES ON REFRIGERATED UNCOOKED PORK AND TURKEY PACKAGED UNDER MODIFIED ATMOSPHERES

Listeria monocytogenes was inoculated onto fresh pork and turkey slice s. Inoculated and control samples were packaged under modified atmosph eres (100% N-2, and 20%/80% and 40%/60% CO2/O-2) or air in plastic bag s of low gas permeability. Samples were stored at 1 and 7C. Samples st ored in air showed a similar microbiological pattern to that usually o bserved in fresh meat stored aerobically. Packaging under modified atm ospheres extended the meat shelf-life. Bacterial growth was strongly i nhibited at 1C, particularly in samples stored under CO2/O-2 enriched atmospheres. Temperature and pH were critical factors for L. monocytog enes growth. This pathogen grew only on pork (initial pH 5.3) packaged in air and stored at 7C. No L. monocytogenes growth was observed at 1 C in any atmosphere assayed. However, growth on turkey (initial pH 6.0 ) was marked at 7C in all atmospheres tested, while at 1C, this bacter ium grew weakly only on samples stored in air.