Effect of refrigerated storage on fillet lipid quality of rainbow trout (Oncorhynchus mykiss W.) fed a diet containing different levels of DL alpha-tocopherol acetate

Abstract

The effect of refrigerated storage at 1 +/- 0.3 degrees C on vitamin E level, fatty acid composition and lipid oxidation of fillets was studied in 3 groups of rainbow trout fed diets supplemented with increasing levels (100, 300 and 500 mg kg(-1) diet, respectively) of alpha-tocopherol acetate as antioxidant. Fish (initial mean weight 131 +/- 1.0 g) were fed experimental diets for 58 days and reached a mean final weight of 299 +/- 6.1 g, with growth differences among the 3 experimental groups being insignificant (P > 0.05). Fillet samples of fish were analyzed fresh (on day 0) or after storage at 1 0.3 degrees C for 9 days. Lipid oxidation was measured using the thiobarbituric acid reactive substances (TBARS) test. Dietary vitamin E levels had a significant effect on fillet alpha-tocopherol levels and TBARS values of fish by the end of 58 days of feeding. At the end of the feeding trial the fillet a-tocopherol levels of fish fed E-100, E-300 and E-500 diets were 30.1 +/- 0.2. 34.3 +/- 0.1 and 40.1 +/- 0.1 mg kg(-1), respectively, and the fillet alpha-tocopherol levels were gradually decreased during the 9 days of storage at 1 0.3 degrees C (P 0.05). However, during the refrigerated storage period, total saturated fatty acid (SFA) concentration slowly increased and total polyunsaturated fatty acid (PUFA) concentration slowly decreased (P < 0.05). Finally. increasing the levels of alpha-tocopherol acetate in the diets from 130 to 580 mg kg(-1) can slow down the level of lipid oxidation in fish fillets during refrigerated storage for 9 days at 1 +/- 0.3 degrees C.