Nutritional quality of food proteins has been considered to exceed the mere supply of amino acids since the emergence of the concept of bioactive peptides, i.e. oligopeptides produced mainly by proteolysis, and behaving like modulators of various biological functions. While many bioactive peptides have been discovered in milk protein hydrolysates, their presence within meat and fish products or during digestion of such products has been very little documented to date. In this context, our objectives were to characterise and identify peptides (< 5 kDa) in fish flesh and beef meat after storage/ageing and cooking, and subsequently during in vivo digestive hydrolysis in pig, in intestinal contents and in portal blood. The peptidic fraction in muscle-foods, made of non-proteinic peptides (carnosine, anserine, glutathione) and of peptides formed during the technological processes (storage and cooking), was dependent on the species and on the process used. In cooked beef meat, where numerous peptides were detected, fragments of structural proteins were identified. Among the large number of dietary peptides found in duodenal and jejunal contents, some were systemically observed and may be bioactive peptides or precursors. Beside carnosine, the absorption of which depending on its concentration in meat, many compounds, probably oligopeptides were released in the portal vein following specific patterns after a meal of top loin or of shoulder.
