effect comparison of two methods of chilling on total microbial load, coliforms count and weight changes of broiler carcass

in this research the effect of two different methods of carcass chilling (immersion and evaporative) in the poultry industrial slaughter line on microbial load and carcass weight changes was studied. for sampling, after evisceration, each carcass weighted and rinsed with 250 ml of sterile water in a plastic bag. 25 ml of rinses water was taken and into sterile scaled container sent to laboratory. after identified of carcasses with tag, them back to slaughter line and sent to chilling tank or evaporative system. considering that the water in evaporative system, after flow on carcass is out than system and don’t contact to carcass again, thus sampling was done in one step only. at the end of chilling, carcasses were weighted and sampled as same as before of chilling. results show that carcass weight mean decrease approximately 5.9 % in evaporative method and increase 5.5, 5.1 and 4.1 percent in the first, middle and end of slaughter, in immersion method respectively and this differences were not significant between before and after of chilling (p>0.05). total count in evaporative method decreased 62.4 percent that had significant difference with immersion method. also total count in first time of immersion method had significant difference with end of the slaughter time (p<0.05). primary coliforms (before of chilling) shown significant different in each of two methods although coliforms change ratio between whole treatment was not significant (p>0.05). the results of this study show that microbial load increase in slaughter line with passing time and water absorption of carcasses in immersion method is more than evaporative method. also carcass discoloration was seen in evaporative method.