Selenium Speciation in Commonly Consumed Thai Seafood Under Different Cooking Methods

Selenium (Se) speciation in seafood is a key determinant of its nutritional value. However, limited data exist on the influence of common cooking methods on Se chemical forms. This study investigated Se speciation in commonly consumed Thai seafood prepared by different cooking methods, namely, fresh (control), boiling, frying, and grilling, using HPLC-ICP-QQQ-MS. Across all samples, Se was predominantly present in organic forms, with selenomethionine (SeMet) identified as the major species, followed by selenocystine (SeCys₂), while inorganic forms (Se(IV) and Se(VI)) were generally below the limit of quantification. Indo-Pacific horseshoe crab (eggs) consistently presented significantly higher SeMet concentrations than all other seafood species across all cooking methods (p < 0.05). In addition, frying and grilling resulted in higher apparent SeMet concentrations compared to fresh and boiled samples in several species (p < 0.05). This increase should be interpreted as a concentration effect associated with moisture loss during high-temperature cooking, rather than a true chemical formation of SeMet. SeCys₂ concentrations varied across species and cooking conditions, with significantly higher levels found in certain crustaceans, such as banana prawn and musk crab, particularly after boiling (p < 0.05). Extraction yields ranged from 77% to 94%, indicating high analytical recovery. Overall, cooking methods influenced the concentration of Se species but did not substantially alter their chemical forms. These findings suggest that commonly consumed Thai seafood is a rich source of bioavailable Se, particularly in the form of SeMet. Further research is warranted to characterize minor Se species and assess their nutritional implications.