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Effect of Pre-slaughter Stress and Short Super-chilling on the Quality of Atlantic Salmon (Salmo salar) Pre-rigor Fillets: Cathepsin B+L Activity, Muscle fibre Detachments and Fillet Texture
HAVBRUK 2008; Tromsø, Norway, 2008-04-07–2008-04-09
We investigated the impact of two biochemical and physical parameters on the quality of Atlantic salmon pre-rigor fillets. Super-chilling (45 minutes, -1.5oC) formed destructive intra- and extra-cellular ice crystals affecting the integrity of the muscle. As a consequence, release of cathepsin B+L from the lysosomes was accelerated, eventually leading to enhanced muscle degradation in the super-chilled fillets. Loss of attachment between muscle fibres evaluated microscopically was positively correlated with the level of cathepsin B+L activity released from the lysosomes to the cytosol in the fish muscle. Long and short pre-slaughter crowding stress (respectively 24h and 20 minutes, density 180 kg/m3) affected fish muscle integrity, also accelerating detachments between muscle fibres, compared to low stress handling of fish. Cathepsin B+L total activity in muscle homogenate is thus expected to be higher in the long stress (and short stress) than in the low stress group, as it was correlated in the super-chilling experiment. This will be checked by further analyses. In both cases, texture of the fillets measured instrumentaly and loss of attachments between muscle fibres and myocommata evaluated microscopically were neither directly affected by the different treatments, nor correlated with the level of cathepsin B+L released from the lysosomes, at least until one week post-mortem. Consequences of super-chilling and pre-slaughter stress on fillet texture and myofibre-myocommata attachments thus may have steped in much later on, during storage time. We concluded that quality of Atlantic salmon pre-rigor fillets was affected by short super-chilling and pre-slaughter crowding stress. This was investigated particularly with the level of cathepsin B+L released from the lysosomes and microscopic observations. Super-chilling needs to be optimized and pre-slaughter stress minimized to assure a high quality of Atlantic salmon pre-rigor fillets.