Summary

Long-term proteolysis of tuna by-products (head, viscera and tail) by the wide spec-trum protease Protamex has been investigated and compared. After hydrolysis, two frac-tions (soluble aqueous phase and insoluble sludge) were collected. Chemical compositions of each fraction and molecular mass distributions of soluble peptides were determined. Degrees of hydrolysis obtained after 12 h of hydrolysis of head, viscera and tail were 32.3, 16.8 and 22.2 %, respectively. Nitrogen recovery in the soluble fractions was 73.6 % for the head, 82.7 % for the viscera and 85.8 % for the tail. Lipid distribution indicated that the majority of lipids remained in the sludge. Such proteolysis appears useful for the produc-tion of very different fractions: one rich in peptides of medium to small molecular mass and poor in lipids, and another one containing the insoluble proteins and the majority of lipids