Growth of Listeria monocytogenes on sliced cooked meat products

During the shelf life (4-6 weeks) of artificially contaminated sliced cooked meat products such as luncheon meat, ham and chicken breast, the growth of Listeria monocytogenes under vacuum was similar to the growth under modified atmosphere (30% CO2/70% N-2) packaged products. The presence of competitors (lactobacilli), even in concentrations 100 times those of L. monocytogenes, only slightly inhibited growth of this pathogen. At the end of the shelf life levels were still 10(7) cfu g(-1). Due to the lower initial contamination, levels in naturally contaminated products were about 10(4) cfu g(-1). To prevent outgrowth of L. monocytogenes to such high levels it is necessary to prevent recontamination during slicing and packaging, and to shorten the rather long shelf life of these products. Due to the low pH of fermented sausage (saveloy) and (raw) Coburger ham the numbers of L. monocytogenes decreased below the detection level. (C) 1996 Academic Press Limited