The effects of stress and storage temperature on the colour and texture of pre-rigor filleted farmed cod (Gadus morhua L.)

This experiment deals with the effects of pre-slaughter stress and storage temperature on muscle pH, fillet contraction, colour and texture in pre-rigor filleted farmed cod fillets. The fish were either sedated with a low dose of MS-222 (14.3 mg L-1) (unstressed groups) or exposed to the air for 3 min (stressed groups) before being submerged in a benzocaine bath (150 g L-1). The fish were then killed by a blow to the head, their gills cut, filleted and finally stored at either 4 or 20 degrees C. The stressed groups had significantly lower pH values after slaughter (pH=7.0) than the unstressed groups (pH=7.3). This difference was maintained until post rigor for the fish stored at 4 degrees C, but at 20 degrees C it was immediately overshadowed by a decrease in pH caused by temperature-dependent processes. The length contraction and changes in registered colour values were more pronounced at both the higher temperature and the higher level of pre-slaughter stress. Again temperature dominated, but significant and consistent effects were registered from stress. No significant effects of stress on texture post rigor were observed. It is concluded that high storage temperature masks the majority of effects caused by pre-slaughter stress on the measured variables. Stress management protocols, however, are important when the fillets are kept at the common storage temperature of 4 degrees C.