The selenium content of staple foods from Malawi and Papua New Guinea

Abstract

Selected samples of raw and cooked staple foods from the Zomba district of Malawi, East Africa ( n = 37), and the Wosera subdistrict of Papua New Guinea ( n = 19) were analyzed for selenium by instrumental neutron activation analysis, using the short-lived 77Se ( t 1 2 = 17.4 s ) isotope. Food samples, previously dried and ground, were irradiated at a neutron flux of 5 × 10 12 neutrons · CM −2 · s −1 using an irradiation/decay/count protocol of 30, 7, and 30 s, respectively. Selenium concentrations were determined by recording the net counts of the 162-keV γ rays emitted by 77Se within the samples. Selenium content was expressed per 100 g of raw or cooked edible portion, on a wet weight basis. Of the Malawian staple foods, animal products such as fish had the highest selenium concentrations (11.1 to 73.2 μg/ 100 g), followed by duck eggs (19.5 μg/ 100 g). Cereals had selenium concentrations ranging from 2.0 to 12.9 μg/100 g; legumes ranged from 0.7 to 6.4μg/100 g; fruits and vegetables were low (0.2 to 1.2 μg/100 g). The staple foods analyzed from Papua New Guinea were mostly plant-based and low in selenium ranging from 0.1 μg Se/100 g for sago to 3.3 μg/100 g for pumpkin tips. Breadfruit seeds, however, contained 10.7 μg Se/100 g. The selenium content of the Malawian foods resembled that of comparable foods grown in countries where the soil is low in selenium. The analyzed staple foods of Papua New Guinea were generally low in selenium.