Yield and approximate composition of <em>in natura</em> and pre-cooked rainbow trout (<em>Oncorhynchus mykiss</em>) (Wallbaum) fillets of different weight

Abstract

The aim of this work was to evaluate the weight classes (CP) and processing form (FP) effects on rainbow trout Oncorhynchus mykiss (Wallbaum) (Salmoniformes, Salmonidae) yield and approximate composition. The assays were carried out in a completely randomized factorial design. The analyzed variables were weight classes (CP₁=300 up to 345g; CP₂= 350 up to 395g and CP₃= 400 up to 445g) and processing form (FP₁= iin natura fillet and FP₂= pre-cooked fillet). The CP and FP showed significant effect on fillet yield, but they didn’t show interaction effect (p > 0.05). The CP₂ class showed higher fillet yield (44.81%) than CP₁ (41.70%) and CP₃ (42.81%). Regarding the processing form, the yield of in natura fillet (44.51%) was higher (p < 0.01) than pre-cooked fillet (41.70%), probably due to the skin percentage in pre-cooked fillet (8.31%), higher than in natura fillet (6.16%) with p < 0.01, as well as to the moisture loss during the processing. Nevertheless, the skin percentage did not differ (p > 0.05) among the analyzed CP. The approximate composition in the CP showed significant effect (p < 0.05) only on the moisture contents in the fillets (CP₁= 73.25%, CP₂= 72.19% e CP₃= 73.03%). The FP analysis of in natura fillets showed higher values (p < 0.01) for moisture (73.69%) and lipids (6.56%) than pre-cooked fillets (71.95% and 5.53%, respectively). Significant effects that (p < 0.01) of the interaction between CP and FP were observed only for moisture contents. The highest moisture content was observed in in natura fillets from classes CP₁ (74.86%) and CP3 (73.90%), although no difference was observed in the pre-cooked class. The contents of crude protein (19.05%) and ash (1.16%) were lower (p < 0.01) than in the pre-cooked fillet (21.79% and 1.35%, respectively).