2D DIGE/MS to investigate the impact of slaughtering techniques on postmortem integrity of fish filet proteins

Two-dimensional difference gel electrophoresis (2D DIGE) was applied to investigate the
impact of slaughtering on the postmortem integrity of muscle tissue proteins in European
sea bass (Dicentrarchus labrax). Three different slaughtering techniques were evaluated:
asphyxia in air (AA), asphyxia in ice (AI), and spinal cord severance (SCS). Principal
components analysis (PCA) revealed a significant divergence of SCS samples, whereas AA
and AI samples, although grouped separately, were less divergent and could be included in
a single asphyxia cluster. In terms of single proteins, the most significant impact was seen
on nucleoside diphosphate kinase B, which was consistently less affected when fish were
slaughtered by SCS as compared to asphyxia. Integrity of the sarcomeric proteins myosin
heavy chain and myosin binding protein C and of the cytosolic proteins fructose
biphosphate aldolase, glyceraldehyde 3-phosphate dehydrogenase, and enolase 1 was
also better preserved upon SCS slaughtering. Most interestingly, the influence on muscle
protein integrity could be detected since the early postmortem phase. In conclusion,
slaughtering by SCS preserves protein integrity better than death by asphyxia, either in
ice or in air. Both asphyxia conditions are comparably more adverse than SCS to muscle
protein integrity, although a general trend favoring AI over AA is observed.