Abstract: The effects of five different cooking methods (boiling, steaming, microwaving, oven baking and frying) on lipid and protein oxidation and their influence on the in vitro protein digestibility of sturgeon fillets were studied. Significant lipid and protein oxidative changes occurred in cooked fish fillets and were much more pronounced in roasted and fried samples. These changes were further reinforced during simulated digestion, especially intestinal digestion. A marked interaction between lipid and protein oxidation was also manifested during cooking and digestion. Furthermore, protein oxidation induced by cooking before digestion had a notable impact on proteolysis during digestion. Roasted and fried samples were less sensitive to pepsin due to polymerization of severely oxidized protein. After the completion of gastrointestinal digestion, there still existed some short peptides in cooked fish, especially roasted and fried fish, which could not be digested thoroughly.

Key words: cooking method, fish, protein oxidation, proteolysis, in vitro digestion