The Effect of Stunning Methods and Season on Muscle Texture Hardness in Atlantic Salmon (Salmo salar L.)

Commercially collected records of Atlantic salmon (Salmo salar L.) muscle texture hardness were used to evaluate the effect of slaughter procedures and seasonality on texture quality. A database collected by Marine Harvest (R) contained flesh hardness records of Atlantic salmon slaughtered at processing plants in Norway from summer 2010 to summer 2011. The fish were slaughtered either by (1) percussion followed by automated bleeding (Percussive) or (2) live chilling with exposure to carbon dioxide (CO2) followed by manual severing gill arches and bleeding (CO2) or (3) live chilling with exposure to CO2 followed by percussive stunning and at the end automated bleeding (CO2 center dot percussive). Hardness in salmon muscle cutlets was measured in Newtons (N) by Materials Testing Machine Zwick 500N. The hardness in salmon varied significantly over the study period (P < 0.05, mixed effect model) and showed the softest value of 21.2 (+/- 0.7) Newton (N) in summer 2011 and hardest 24.1 (+/- 0.2) N in autumn 2010. Slaughter procedures had a significant effect on salmon muscle hardness (P < 0.05, mixed effect model), where percussion followed by automated bleeding resulted in the hardest value (24.0 +/- 0.4 N) as compared with CO2 stunning (21.8 +/- 0.2 N) and combination of CO2 and percussive stunning (23.1 +/- 0.15 N). CO2 is suspected as a causal factor in accelerated postmortem softening of the salmon muscle. Practical Application Commercial use of CO2 in combination with live chilling results in accelerated postmortem softening of the muscle tissue in salmon and should be avoided.