Cyclic Heat Stress in Broilers and Their Effects on Quality of Chicken Breast Meat

ABSTRACT Background: The growing concern of the effects of high temperatures in the production of broilers, apart from the consistent increase of the consumption of chicken meat in Brazil and in the world and form the demands of consumers and industries increase the need for comprehensive studies on organoleptic characteristics of this meat, such as color and loss of water drip (drip loss). In this scenario, the objective of this research was to investigate the effects of cyclic heat stress on color and drip loss of chicken breast of broilers at different growth stages. Materials, Methods & Results: A group of 840 1-day-old CobbAvian48 ® broiler male chicks was housed in a shed, in 24 boxes with 35 birds each according to a completely randomized design. The broilers were reared under thermal comfort for 15 days. On the 16 th day the shed was divided in sections with the following thermal environments: Control -Broilers reared under natural temperature and humidity conditions between day 16 and 42 (C 16-42), and broilers submitted to cyclic heat stress between day 16 and 21 (CHS 16-21), day 22 and 42 , and between day 16 and 42 . Stress was imposed from 12:00 noon to 1:00 pm, with temperature above the maximum recommended for the lineage. On day 42, one broiler of each box weighing close to the mean weight on a box basis was slaughtered and the breast meat removed, totaling 24 breasts. Color was analyzed using the following visual standard: 1 = PSE meat (pale, soft, exudative), 2 = normal meat, and 3 = DFD meat (dark, firm, dry). Chicken breasts were visually compared to the standard. To determine drip loss, a meat fragment was removed, weighed, and placed in a nylon-poly plastic bag, which in turn was placed in polyethylene plastic packaging properly labeled. After, these were hung in a refrigerator for 48 h at controlled temperature of 4-8°C. Drip loss data were analyzed using ANOVA, and the means were compared using the Tukey test at 5%. Color data were evaluated using the Kruskal-Wallis test followed by the SNK test. Spearman analysis was used to assess the correlation between drip loss and color. Mean drip loss did not vary between thermal environments (P > 0.05). Regarding color, the broilers in the CHS 22-42 group differed from the C 1-42 group (P = 0.02). There were also significant differences between the CHS 22-42 group and the CHS 16-42 group (P = 0.03). The linear correlation between drip loss and color was significant, negative and of midrange intensity (r = -0.41), which indicates that, when the drip loss increases, the score for color decreases, or vice-versa. Discussion: One-hour cyclic heat stress accelerates rigor mortis in broilers, and may result in PSE meat. The alteration of chicken breast color is directly influenced by the time the broilers are submitted to the heat stress. The quality parameter drip loss may be influenced by environmental factors, such as cyclic heat stress; however, this study showed that there is no direct interference. In this sense, evidence of this interference in loss of water in chicken breast is important, because this factor influences the quality and yield of processed products, such as brine-preserved, skin-encased, and cook-in-bags food items. The use of heat stress for 1 h daily in different periods of life does not affect the loss of water in chicken breast, but it may alter the color