Effect of selenite on organic selenium speciation and selenium bioaccessibility in rice grains of two Se-enriched rice cultivars

The accumulation of organic selenium (Se) in grains is helpful in understanding its bioaccessibility in various Se-enriched rice cultivars after soil selenite treatments. In the present study conducted with two rice cultivars, the organic Se as well as the glutelin-derived Se and the selenomethionine (SeMet) percentage in grains increased with soil Se levels. The available Se that was detected in the forms of SeMet (similar to 40%) and selenite (similar to 12%) accounted for more than 50% of the total Se in grains, and no significant differences were observed between the two rice cultivars (P > 0.05). Simulated gastrointestinal digestion showed that the digested grain SeMet increased with the soil Se treatment levels, whereas there were minimal changes in the percentages of selenite in the grain. Furthermore, approximately half of the available SeMet was derived from the grain glutelin. These results suggest that the non-glutelin-derived Se in rice should be further studied.