Study of the proteolysis and cathepsin D activity of commercial dry-cured Iberian and Serrano hams

Abstract

Physicochemical characteristics, proteolysis, and cathepsin D activity of the Semimembranosus and Biceps femoris muscles from commercial Iberian and Serrano hams were evaluated. Total nitrogen, sodium chloride, fat, and amino acid nitrogen contents were the only parameters of physicochemical composition and nitrogen fractions that enabled Iberian ham to be differentiated from Serrano ham in the two muscles considered. A wide variety of polypeptides in sarcoplasmic and myofibrillar protein fractions were found in the Semimembranousus and Biceps femoris muscles from Serrano and Iberian commercial samples. The sarcoplasmic proteins present in both muscles from both ham varieties had molecular weights of 80, 50, 45 (creatine kinase), 30 (phosphoglycerate mutase), 18, 16 (myoglobin), and 9 kDa. The common myofibrillar proteins in both muscles from both ham varieties had molecular weights of 102 (a-actinin), 90, 80, 60, 50, 35 (Tropomyosin), 30, 20 (C-troponin), 15 (Myosin light chain III), and 11 kDa. The protein profile showed that, in general, the myofibrillar protein fraction underwent more intense proteolysis than the sarcoplasmic protein fraction, giving rise to a larger number of low-molecular-weight peptides. Residual cathepsin D activity in the samples was very low, with no differences between either the muscle tissues or the ham varieties, indicating that the hams are relatively stable, as regards to proteolysis, once they have reached the marketplace.