Effect of time on performance of natural and synthetic antioxidants (ascorbic acid and butylated hydroxyanisole) of painted sweetlips (Diagramma pictum) fillet during the frozen period

The aim of this study was to compare the antioxidant activities of ascorbic acid and butylated hydroxyanisole on biochemical deterioration and tasting indexes of painted sweetlips, Diagramma pictum, fillet under frozen condition (-18 C) for a period of 4 months. The fish fillet was treated with 1.5 % ascorbic acid, 1.5% butylated hydroxyanisole and a combined treatment with their 0.5% concentrations. The fat deterioration indices including peroxide value, free fatty acids, thiobarbituric acid, volatile nitrogenous bases, and by the intuitive evaluation were monthly measured after freezing. The results indicated that the peroxide value in the treatment of 1.5% butylated hydroxyanisole and 1.5 % ascorbic acid were higher than that in the combined treatment. However, peroxide value in all treatments didn’t cross the limited level of 10 meq O2 kg-1. Minimum average of thiobarbituric acid index was found in the combined treatment (0.593 mg MDA kg-1) indicating the effectiveness of this treatment in controlling the deterioration index (p<0.05). Fatty acids index in 1.5% ascorbic acid treatment was significantly higher than other treatments (p<0.05). At the end of the experimental period, the combined treatment limited the amount of volatile nitrogenous bases to the lowest level compared with the other treatments (p<0.05). The maximum amount of volatile nitrogenous bases was recorded in 1.5% butylated hydroxyanisole treatment. However, the volatile nitrogenous bases in all treatments did not cross the limited value of 30-35 mg 100 g-1. Findings of the present study indicated that the combined treatment had more ability to inhibit the deterioration indexes of fat compared with the other treatments. In case of intuitive evaluation, the combined treatment (0.5% ascorbic acid +0.5% butylated hydroxyanisole) had the best results with significant differences in three factors of taste, tissue and color compared to the other treatments (p<0.05).