Effect of carbon monoxide for Atlantic salmon (Salmo salar L.) slaughtering on stress response and fillet shelf life

• CO and percussive stunning/slaughtering were applied in salmon.
• Salmon were exposed to CO in water for 8 or 20 min.
• Fish behaviour, some blood and fillet quality parameters were analysed.
• CO induced changes in catecholamine's levels and rigor mortis evolution.
• Fillet colour and drip loss value were also affected by CO treatment.

The effect of carbon monoxide (CO) as stunning method in Atlantic salmon (Salmo salar L.) on stress indicators (adrenaline, A; noradrenaline, NAD) and on fillets quality during the shelf life has been investigated. The CO was dissolved into tanks with salmon for 8 and 20 min to obtain fish groups CO8 and CO20, respectively. These groups were compared to a non-stressed control group (C). All the fish were hauled out from the tank and killed by percussion. Adrenaline content of CO20 group was 1.8 and 1.7-fold higher than CO8 and C groups respectively (P < 0.001), which exhibited similar values. Noradrenaline content was higher in CO20 than in C group (8.1 vs. 5.4 ng/ml plasma; P < 0.0001). The CO treatment resulted in a small significant increase in lightness and yellowness, not altering the overall “natural” colour of the fillet. CO treatment caused a rapid onset of rigor mortis and a small but significant increase in drip loss (P < 0.05).