Speciation of selenium in fresh and cooked commonly consumed fish in Thailand

Abstract

Fish are an important protein source commonly consumed by the Thai people due to their ready availability and affordability in local markets. Fish are also good sources of selenium (Se), an essential trace element that plays a key role in human health. This study investigated the ten most commonly consumed freshwater and marine fish in Thailand in terms of their chemical forms of Se as prepared fresh, boiled, or fried. Organic forms of Se including selenomethionine (SeMet) and selenocystine (SeCys2) as well as the inorganic forms of selenate (Se[VI]) and selenite (Se[IV]) were assessed using High-Performance Liquid Chromatograph coupled with Plasma Triple Quadrupole Mass Spectrometry. All fish species had Se(VI) and Se(IV) below the limit of detection. For fresh fish, mixed results indicated the major forms were SeMet and SeCys2. However for boiled and fried fish, SeMet was the major Se form. Fresh and fried longtail tuna were significantly higher in SeMet compared to the other fish (p < 0.05). Boiled short-bodied mackerel was significantly higher in SeMet compared to the other fish (p < 0.05). For SeCys2, fresh giant sea perch and fresh Indo-pacific Spanish mackerel, boiled short-bodied mackerel, fried striped snakehead, and fried Indo-pacific Spanish mackerel had significantly higher SeCys2 concentrations compared to the other fish using the same cooking methods (p < 0.05). Overall, therefore, most fish species commonly consumed in Thailand contained organic Se (SeMet and/or SeCys2) as the major form of Se.