Effect of soybean meal-based diets on the product quality of rainbow trout fillets

This study investigated the long-term effects of soybean meal (SBM)-based diets on rainbow trout quality. Two levels of SBM inclusion diets, 20% and 40%, were employed and compared with a fish meal control diet. Rainbow trout were fed one of the three diets for 6 mo, then harvested and filleted. Proximate composition, colour, lipid oxidation and sensory quality of the fillets were evaluated. Thiobarbituric acid reactive substances (TBARS) and headspace propanal in ground fillets stored at 4 degrees C were measured over a 9-day period. Tristimulus colour was measured on day 2 and day 13 of refrigerated storage. sensory evaluation included discriminatory (difference) and affective (acceptance) testing. TBARS and propanal in the trout fed the highest (40%) SBM level were significantly lower than in the control and trout fed the 20% SBM diet. Significant differences in colour were also recorded during the refrigerated storage. Sensory difference testing revealed a significant difference between the trout fed the 40% SBM and the control. No significant difference were observed in the acceptability ratings of trout fillets from the three different dietary treatments.