Effects of three different stunning/slaughtering methods on physical, chemical and sensory changes in rainbow trout (Oncorhynchus mykiss)

BACKGROUND Electrical stunning (E) and asphyxia in the air (A) are two common stunning/killing methods for fish. However, they can stress the fish and affect flesh quality, so an alternative should be found. The present study aimed to evaluate the effects of a carbon monoxide asphyxia (CO) compared to E and A on the evolution of post‐rigor mortis changes of rainbow trout (Oncorhynchus mykiss) fillets related to chemical, textural and sensorial properties during storage time. RESULTS Fish fillets from the E group showed higher pH (p<0.05) than the A ones, both at time of rigor resolution (TRR0) and from TRR4 till TRR7 (7 days after rigor resolution, which corresponded to 10 days post‐mortem), with the CO group being always intermediate. The CO treatment ensured effectively the lowest yellowness index (b*) to the fillets, even if only at TRR2 and TRR5. Lipid oxidation and texture profile analyses were unaffected. The sensory analysis revealed that the CO fillets had the lowest odour intensity and the highest juiciness scores (p<0.05). Among the others, the sensory descriptors were the most discriminant variables of fillets from the differently stunned animals, as resulted by the Canonical Discriminant Analysis. CONCLUSION The carbon monoxide stunning/slaughtering method could be applied on rainbow trout without detrimental effects on physical, chemical and sensorial characteristic of the fish flesh.