Impact of fish growing conditions and cooking methods on selenium species in swordfish and salmon fillets

This study evaluates the effect of fish growing conditions (captured fisheries or aquaculture) and cooking methods (fried, oven-baked and smoked) on selenium species distribution In fish fillets (salmon and swordfish). Fillets from 10 individual fishes for each fish species were analyzed. Selenium speciation was examined using HPLC-ICP-MS. Selenium in fillet samples was mainly present as organic selenium (around 93% of selenium content). Selenomethionine (SeMet) and selenocystine (SeCys(2)) were the main species found in salmon, regardless of its growing conditions (farmed or wild). However, SeCys(2) was found at a higher concentration in wild salmon fillets. Concerning swordfish, SeMet, SeCys(2) and selenomethylselenocysteine (SeMetSeCys) were detected and quantified. New selenium species were not produced when fillets were cooked. However, differences in selenium species distribution were observed for some fishes and/or treatments. Baking led to a notable increase of SeMetSeCys in swordfish (68% of the total selenium), in comparison with the amount of SeMetSeCys found in raw fish (17% of total selenium), whereas a notable decrease of SeCys(2) occurred when salmon was submitted to the different cooking techniques. In contrast, smoked salmon provided a selenium species distribution similar to that of raw farmed salmon.