The effect of chilling in cold air or ice water on the microbiological quality of broiler carcasses and the population of Campylobacter

Cold air or ice water can be used to chill poultry carcasses after slaughter. The objective of this study was to compare the effect of 2 chill methods on broiler carcass bacteria. Broiler carcasses were cut in half along the dorsal-ventral midline; one half was subjected to an ice-water immersion chill in an agitated bath for 50 min, whereas the reciprocal half was subjected to an air chill in a 1 C cold room for 150 min. Total aerobic bacteria, coliforms, Escherichia coli, and Campylobacter were enumerated from half-carcass rinses. Species of Campylobacter isolates was determined by a commercial PCR method, which was followed by molecular subtyping with pulsed-field gel electrophoresis and determination of antimicrobial susceptibility to 9 drugs. Although significantly fewer of each bacterial type were detected per milliliter from immersion-chilled carcasses than from air-chilled car-casses, in each case the difference was less than 1 log(10) cfu/mL. Chilling method did not affect species; both Campylobacter jejuni and Campylobacter coli were recovered. Results of pulsed-field gel electrophoresis subtyping did not suggest that either chilling method selected for any specific subtypes; most subtypes were found on carcass halves used for both the air chill and water immersion chill. Resistance to 2 antimicrobial drugs was noted in 9 C. coli isolates, 6 from air-chilled carcass halves and 3 from immersion-chilled carcass halves. These data showed that immersion-chilled carcasses had lower numbers of bacteria; however, the difference was not large and may have been due to simple dilution. Both methods were effective for lowering carcass temperature, and neither chilling method seemed to select for specific species, subtypes, or antimicrobial-resistant Campylobacter.