Effects of dietary restriction on post-mortem changes in white muscle of sea bream (Sparus aurata)

Four lots of sea bream were fed with different ration levels (R100, R75, R50, and R25, corresponding to 100, 75, 50 and 25%, respectively, of the standard ration fed in the fish farm), in order to assess the effects of a 30-day pre-slaughtering period of feed restriction on the textural characteristics of the edible muscle of farmed sea bream (Sparus aurata). Results showed that food restriction over 50% influenced negatively total body and individual organ weights. Fish in a good nutritional condition presented lower muscle pH and poorer muscle characteristics, showing soft texture and decreased water holding capacity (WHC). When the intake was moderately restricted (R75), a positive influence on pH and WHC of muscle was found. A 50% reduction of the ration size also delayed muscle softening during cold storage; whereas, a more severe restriction (R25) did not improve this parameter. Electrophoretic studies showed minor changes in the relative optical density of sarcoplasmic and myofibrillar protein fractions attributable to the different ration sizes assayed. These results suggest that the main contributing factor to the observed enhancement in muscle texture due to feed restriction is likely the decrease of lipid deposits in the structural components of the muscle.