Intensity of lipid oxidation and formation of cholesterol oxidation products during frozen storage of raw and cooked chicken

Raw and cooked chicken breasts were stored at -18 degreesC for 3 months under aerobic and vacuum conditions, and the intensity of lipid oxidation and the formation of COP (cholesterol oxidation products) were studied. Raw samples showed low COP levels (4.60-7.40 mug g(-1) fat), TBARS (thiobarbituric acid reactive substances) levels (0.01-0.03 mg kg(-1)) and peroxide values (not detected) under both aerobic and vacuum conditions. Cooked samples (grilled and roasted) showed TBARS levels of 0.36-0.99 mg kg(-1) in aerobic conditions and 0.21-0.70 mg kg(-1) in vacuum conditions, whilst peroxide levels reached 38-40 and 19-23 meq O-2 kg(-1) in samples stored under aerobic and vacuum conditions respectively. Total COP levels in grilled and roasted samples were 28.91 and 39.34 mug g(-1) fat in aerobic packaging and 4.90 and 20.24 mu g g(-1) fat in vacuum packaging respectively. Significant correlations were found between the lipid oxidation parameters and cholesterol oxidation indices. In general, TBARS were better correlated with total COP than with only 7-ketocholesterol. Vacuum packaging was particularly efficient in slowing down the oxidation process during frozen storage of cooked samples. (C) 2004 Society of Chemical Industry.