Starvation prior to slaughter in Atlantic salmon ( Salmo salar) : II. White muscle composition and evaluation of freshness, texture and colour characteristics in raw and cooked fillets

Abstract

Muscle composition and quality characteristics of fillets were investigated in triplicate groups of 5-kg Atlantic salmon starved at low water temperatures for 0, 3, 7, 14, 30, 58 or 86 days prior to slaughter. White muscle and raw fillets were analysed at slaughter and after 4 and 12 days of ice-storage of gutted fish, whereas sensory analyses of cooked fillets were performed after storage for 13–16 days. At slaughter, the level of glycogen in white muscle decreased with the length of starvation. After 4 and 12 days of ice-storage, lactate and glycogen levels decreased and pH increased in white muscle with increasing starvation time. The K-value, determined after 4 and 12 days of ice-storage, decreased as the duration of starvation increased. Trimethylamine was not detected in white muscle. Sensory analyses showed that cooked fillets from groups starved for 86 days had less fresh flavour than that of groups starved for 30 days or less. The fillets of groups starved for 30 days had significantly higher acidulous flavour compared with that of groups starved for 0–14 days, whereas groups starved for 58 or 86 days had significantly less acidulous flavour than all other groups. The sensory assessed hardness of cooked fillets was significantly lower in groups starved for 86 days vs. those starved for 0, 14 or 30 days. In contrast, instrumental texture analyses of raw fillets, after 4 days of ice-storage, showed that the force against compression (at 5 mm) was higher in groups starved for 58 or 86 days than in those starved for a shorter time. Although astaxanthin concentration was not significantly affected by starvation time, instrumental colour analyses (CIE 1976) of raw fillets revealed changes in lightness ( L*) and yellowness ( b*). Although starvation produced some changes in white muscle composition, the rather marginal differences in freshness, texture and colour characteristics of raw or cooked fillets when starvation time varied from 0 to 86 days, suggest that starvation is a rather weak tool for changing fillet quality in Atlantic salmon.