The microbiological profile of chilled and frozen chicken

To determine the effect of different refrigeration and freezer temperatures on the microbiological profile of chicken, 50 commercially processed broiler chickens were each split in half on the day of processing. Equal groups were held at 4, 0, -4, -12, and -18 degrees C (40, 32, 26, 10, and 0 degrees F), respectively for 7 days. One half of each group was then transferred to a 0 degrees F holding chamber for an additional 7 days. Carcass halves were rinse sampled with 100 ml of phosphate-buffered saline and the diluent sampled for mesophilic, psychrotropic, coliform, and salmonellae counts after the initial 7 days at different temperatures and after 7 additional days at -18 degrees C. Ten carcass halves were sampled on the day of processing to give baseline counts. Mesophilic bacteria counts/ml were about log 4.6 on day 0, increased by 2 log after 7 days on carcasses held at 4 degrees C, and were unchanged at all other storage temperatures. Psychrotropic counts/ml were about log 3.6 on day 0 and increased during the initial 7 days by about 3.9, 1.9, and 1.4 logs, respectively on carcasses held at 4, 0, and -4 degrees C and had less than 1 log increase at -12 and -18 degrees C. Coliform counts were about log 2.2/ml on day 0 and had declined to about log 1.5/ml or less by day 7 for all storage temperatures. Escherichia coli counts/ml were about log 2 on day 0 and were reduced about 1 log or more at other storage days. Salmonellae counts were about log 1.5 on salmonellae-positive carcasses and did not change appreciably at any storage temperature. No counts for any organism significantly changed after placement at -18 degrees C.