Use of two-dimensional electrophoresis to evaluate proteolysis in salmon (Salmo salar) muscle as affected by a lactic fermentation

Two-dimensional electrophoresis was used to study proteolysis in salmon fil lets inoculated or not with the starter culture Lactobacillus sake LAD. Pro tein fragments appeared increasingly with time in both samples, indicating that the main quantitative changes were due to endogenous enzymes. In the m ost acidic zone (pI = 4-6.20) particularly, proteolysis was overall indepen dent from processing. In contrast, fermentation had a significant effect in the pH range 6.20-8.35, suggesting a specificity of the bacterial protease s of L. sake toward alkaline to slightly acidic proteins;. Furthermore, fra gments surrounding tropomyosin (apparent pi = 4.70) appeared in fermented s amples, indicating that the protein may be a suitable substrate for the met abolism oft. sake LAD.