Water Absorption and Temperature Changes in Poultry Carcasses during Chilling by Immersion

The temperature profile and water absorption of chicken carcasses during the chilling process by immersion was investigated. The experiments were realized in a slaughterhouse that uses a pre-chiller and chiller operating by the immersion-rotation system in counter flow. Temperature gradients, in the entrance of the coolers, were higher in the pre-chiller than in the chiller, and the rates of heat exchange decreased as the carcass moves forward in each cooler. The influence of the immersion time (18, 22, and 27 min), period interval of ice addition (3 and 5 min) and the number of turbines used in the injection of air (1 or 2) on the temperature of carcasses leaving the pre-chiller was evaluated through a factorial design. The results indicated that the immersion time and the number of turbines were significant factors influencing the final temperature of the carcasses. Interactions among the time interval to ice addition with the time of immersion and this last with the number of turbines were also significant. The percentages of water absorption in the pre-chiller were between 2.0 and 4.5%. The best conditions were: 27 min for immersion time, 5 min time interval to ice addition, and injection of air through two turbines, which corresponded to 14.6 degrees C and 4.1% of water absorption. In this condition, the temperature and water absorption of the carcasses leaving the chiller were 5.4 degrees C and 6.8%, respectively. Refrigeration of poultry carcasses is one of the most important factors to reduce the growth of spoilage microorganisms and prolongs the shelf life of the product. Investigation of optimal conditions for chilling carcasses is an aspect of utmost relevance for meat quality.