Inhibition of lipid oxidation in long-term frozen stored chicken meat by dietary oregano essential oil and α-tocopheryl acetate supplementation

The antioxidative effect of dietary oregano essential oil and alpha-tocopheryl acetate supplementation on susceptibility of chicken breast and thigh muscle meat to lipid oxidation during frozen storage at -20 degreesC for 9 months was examined. Day-old chickens (n = 80) were randomly divided into four groups, and fed a basal diet containing 30 mg alpha-tocopheryl acetate kg(-1) feed as control, or basal diet plus 200 mg alpha-tocopheryl acetate kg(-1) feed, or basal diet plus 50 or 100 mg oregano essential oil kg(-1) for 38 days prior to slaughter. Lipid oxidation was assessed by monitoring malondialdehyde (MDA) formation with third-order derivative spectrophotometry, after zero and 7 days of refrigerated storage at 4 degreesC following 1, 3, 6 and 9 months of frozen storage. Results clearly demonstrated that all dietary treatments had a major impact on the oxidative stability of broiler meat. Dietary oregano essential oil supplementation at the level of 100 mg kg(1) feed was significantly (P less than or equal to 0.05) more effective in reducing lipid oxidation compared with the level of 50 mg oregano essential oil kg(-1) feed and control, but less effective (P less than or equal to 0.05) compared with alpha-tocopheryl acetate supplementation. Thigh muscle was found to be more susceptible to oxidation compared to breast muscle, although the former contained alpha-tocopherol at markedly higher levels. Mean alpha-tocopherol levels in muscle samples decreased during the frozen storage, the decrease being sharper between 1-3 months and 3-6 months of frozen storage for breast and thigh muscle samples, respectively. (C) 2002 Elsevier Science Ltd. All rights reserved.