During the shelf life (4-6 weeks) of artificially contaminated sliced
cooked meat products such as luncheon meat, ham and chicken breast, th
e growth of Listeria monocytogenes under vacuum was similar to the gro
wth under modified atmosphere (30% CO2/70% N-2) packaged products. The
presence of competitors (lactobacilli), even in concentrations 100 ti
mes 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 contam
inated products were about 10(4) cfu g(-1). To prevent outgrowth of L.
monocytogenes to such high levels it is necessary to prevent recontam
ination during slicing and packaging, and to shorten the rather long s
helf life of these products. Due to the low pH of fermented sausage (s
aveloy) and (raw) Coburger ham the numbers of L. monocytogenes decreas
ed below the detection level. (C) 1996 Academic Press Limited