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Effects of Super-Chilling on Quality of Atlantic Salmon Pre-Rigor Fillets: Analyses of Cathepsin Activity and Muscle Histology

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Kjetil Aune

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kjetil.aune@nofima.no

37th WEFTA Annual Meeting. Seafood:Source of Health and Well-Being.; Lisboa, Portugal, 2007-10-23–2007-10-27

Bahuaud, Diane; Thomassen, Magny S.; Mørkøre, Turid; Mørkøre, Turid; Veiseth-Kent, Eva; Langsrud, Øyvind; Langsrud, Øyvind; Sinnes, Kristin; Ofstad, Ragni

The experiment is part of a larger study where the aim was to investigate the impact of super-chilling on quality parameters of pre-rigor salmon fillets. Twenty-four Atlantic Salmon (Salmo salar) raised at AKVAFORSK research station (Averøy, Norway) were used to investigate proteolytic activity and muscle structure development of super-chilled and ice stored pre-rigor fillets. The fish were starved for five days before they were killed by percussive stunning followed by gill cutting and consequent bleeding in a tank with running seawater. The fish (average body weight 5 kg) were filleted immediately after slaughter and either super-chilled to -1.5°C for 40 minutes and then packed on ice in standard styrofoam boxes (n=12), or packed the same way without previous super-chilling (n=12). Cathepsin B+L analyses 0, 6, 12, 24, 48 and 144h after slaughter in the lysosomal fraction of the fish muscle, showed a release of enzymes with time for both super-chilled and chilled fish. For the super-chilled fish, the release of cathepsins from lysosomes started immediately after slaughter, while in the chilled fish, it started only 24h after slaughter. These results suggest that super-chilling accelerated lysosome breakage in the fish muscle, releasing degradation enzymes. As a consequence, super-chilling seemed to accelerate fish muscle degradation. Histological analyses of the muscle showed results in accordance with cathepsin analyses, with not only myofibre-myofibre and myofibre-myocommata detachments, but also degradation of the muscle cells themselves, due to the presence of ice crystals, particularly in the upper layer of the super-chilled fillets. In our experiment, super-chilling seemed to have negative effects on some quality parameters of salmon fillets. It is important that the method for super-chilling is further optimised in order to assure maintenance of superior fillet quality. The experiment is part of a larger study where the aim was to investigate the impact of super-chilling on quality parameters of pre-rigor salmon fillets. Twenty-four Atlantic Salmon (Salmo salar) raised at AKVAFORSK research station (Averøy, Norway) were used to investigate proteolytic activity and muscle structure development of super-chilled and ice stored pre-rigor fillets. The fish were starved for five days before they were killed by percussive stunning followed by gill cutting and consequent bleeding in a tank with running seawater. The fish (average body weight 5 kg) were filleted immediately after slaughter and either super-chilled to -1.5°C for 40 minutes and then packed on ice in standard styrofoam boxes (n=12), or packed the same way without previous super-chilling (n=12). Cathepsin B+L analyses 0, 6, 12, 24, 48 and 144h after slaughter in the lysosomal fraction of the fish muscle, showed a release of enzymes with time for both super-chilled and chilled fish. For the super-chilled fish, the release of cathepsins from lysosomes started immediately after slaughter, while in the chilled fish, it started only 24h after slaughter. These results suggest that super-chilling accelerated lysosome breakage in the fish muscle, releasing degradation enzymes. As a consequence, super-chilling seemed to accelerate fish muscle degradation. Histological analyses of the muscle showed results in accordance with cathepsin analyses, with not only myofibre-myofibre and myofibre-myocommata detachments, but also degradation of the muscle cells themselves, due to the presence of ice crystals, particularly in the upper layer of the super-chilled fillets. In our experiment, super-chilling seemed to have negative effects on some quality parameters of salmon fillets. It is important that the method for super-chilling is further optimised in order to assure maintenan