Selenium bioaccessibility in rice grains biofortified via soil or foliar application of inorganic Se

Abstract

Selenium (Se) is a micronutrient for humans, and its deficiency is related to various diseases. Recent studies have proposed strategies to increase Se intake, especially using selenium biofortification in staple foods. However, few investigations shed light on the chemical species and the bioavailability of Se in cereal grains, including rice, one of the most important staple foods worldwide. This study aimed to determine the bioaccessible fractions of Se in rice grains biofortified with inorganic Se species using an in vitro sequential extraction method to simulate human digestion. Samples and extracts were submitted to microwave-assisted acid digestion, and total/bioaccessible Se levels were determined by DRC-ICP-MS. Accurate Se quantification was achieved using matrix-matching calibration. Rice biofortification via foliar application increased Se levels in the bioaccessible fraction more effectively than soil applications. Bioaccessible Se represented, on average, 61 ± 5 % of the total levels. Of the total Se content in rice, 44 ± 4 % was extracted in the gastric step, which is where most protein-bound bioaccessible selenium is degraded. Biofortification with inorganic forms of Se effectively increases the bioaccessible content of this element in food. Still, the amount to be applied must be corrected based on the bioaccessible fraction of the nutrient in rice grains.