Effects of different stunning/slaughter methods on frozen fillets quality of cobia (Rachycentron canadum)

The aim of this study was to evaluate the influence of stunning/slaughter methods on the animal welfare aspects and on the physical and chemical parameters of frozen cobia (Rachycentron canadum) meat, during the frozen storage. Fish (n = 30 per treatment) were stunned electronarcosis, by hypothermia and CO2 narcosis, then slaughtered by gill cutting and stored at -18 degrees C for 180 days. During stunning/slaughter, water quality and the time to reach clinical indicators of unconsciousness were observed. During the storage period, every 60 days, samples were taken and analysed for pH, total volatile base nitrogen (TVBN), thiobarbituric acid reactive substances (TBARS), protein (actin and myosin) denaturation, fatty acid composition, colour (L*, a*, and b*), texture, drip loss (DL), cooking loss (CL) and water holding capacity (WHC). The time to reach unconsciousness resulted faster (2 s) when electronarcosis was applied, while the times were longer with hypothermia and CO2 narcosis (17.5 min and 48 min, respectively). TVBN, DL, TBARS, texture, actin, myosin, pH, L*, a*, and b* were not affected by the stunning methods while CL was significantly higher in fillet of fish stunned by electronarcosis not altering the shelf life of the fillets. Based on the behaviour of the parameters analysed, electronarcosis seemed to be an adequate stunning method for cobia, since promoted fast unconsciousness and it did not compromise flesh quality.