Effect of various gas atmospheres on the growth and survival of Campylobacter jejuni on beef

Pieces of fresh beef were inoculated with three strains of Campylobacter jejuni. The meat was then allocated to three treatments: (a) vacuum packaged, (b) packaged in an atmosphere of 20% CO2 + 80% N2, and (c) packaged into sterile Petri dishes in anaerobic cultivation boxes, which were filled with a gas mixture of 5% O2 + 10% CO2 + 85% N2. The packaging material in the first two treatments was PA 80/PE 100-PE 100/PA 80/PE 100. The survival of Campylobacter cells was followed at 37 degrees C, 20 degrees C and 4 degrees C for 48 h, 4 days and 25 days, respectively. At 37 degrees C the counts of two Campylobacter strains increased in each package treatment for 48 h. At 20 degrees C and at 4 degrees C the counts of the same two strains decreased by 1 to 2 log units and 0.5 to 1 log unit, respectively, during storage. The survival of the two strains was about the same in all package treatments. The third strain was the most sensitive of the strains studied. At 37 degrees C its numbers increased only in the optimal gas atmosphere; at 20 degrees C the strain was not detectable after 24 to 48 h storage and at 4 degrees C after 4 days storage. The aerobic plate counts were determined for all samples at the same time as Campylobacter counts. The high indigenous bacterial numbers of the meat samples did not appear to have a great effect on the survival or growth of campylobacters.