Physico-Chemical Traits of Raw and Cooked Fillets of Rainbow Trout(Oncorhynchus Mykiss)from Different Strains and Farms

A solution for fillet quality: Slaughter age's effect on protein mechanism and oxidation

Physico-chemical properties of fish flesh are reliable predictors of fillet quality and nutritional value. In our study, the age-related variations of the chemical composition, pH, water activity (aw), water holding capacity (WHC), color and texture analysis, protein thermal stability, myofibrillar fragmentation index (MFI), glycogen content, protein oxidation and protein profiles were investigated in Oncorhynchus mykiss (rainbow trout) fillet. The results revealed that protein denaturation temperatures (Tmax1 and Tmax2) decreased by 2 % and 11.6 % depending on fish age. Tmax1 and Tmax2 values in the same groups were raised 71 % at 11 months' fish and this increase was 58 % at 23 months' fish. An age-related reduction by 66.6 % and 31.25 % was noticed for protein oxidation markers sulfhydryl groups and disulfide bonds. MFI value increased by 86.6 % connected with age. The characteristics of fish meat quality are complex and are influenced by various factors that affect the degree of freshness of the product and its acceptance in the market. Taking into account the different demands of the consumer, this study has shown that age at slaughter has an impact on final product quality and that the recommended age at slaughter, taking into account market weight, positively affects meat quality.

Can the inclusion of black soldier fly (Hermetia illucens) in diet affect the flesh quality/nutritional traits of rainbow trout (Oncorhynchus mykiss) after freezing and cooking?

Physical and chemical parameters of rainbow trout fillets were tested during 120 days of frozen storage and following cooking. The fillets were obtained from rainbow trout-fed diets where dietary fishmeal was substituted with Hermetia illucens meal at 0, 25 and 50% inclusion levels, corresponding to control (C), Hi25, and Hi50 diets. Variations in quality traits of fillets emerged after 30 days of frozen storage, however they remained almost unchanged for the other 90 days. Increasing levels of H. illucens did not affect pH, shear stress, colour and water holding capacity of fillets. Saturated fatty acids were highly present in Hi50 samples, the polyunsaturated and some monounsaturated ones were higher in C than Hi50, whereas Hi25 always assumed intermediate contents in raw and cooked samples. A medium substitution at the 25% seemed to be the most practical application of insect meal in order to not modify too much the fillets characteristics.