Preparation and characterization of starches selenylated with different selenium content

Selenium plays a crucial role in human health. We previously developed a straightforward method for obtaining selenylated starch granules. However, we have yet to prepare and characterize selenylated starch with varying selenium content, particularly regarding its multi-scale structures and its selenium delivery properties in the gastrointestinal tract. This study synthesized selenylated starch granules with different selenium contents and characterized their structures and physicochemical properties. The yield and selenium content of selenylated starch gradually decreased and increased, respectively, with increasing water content, acetic acid content, selenous acid content, reaction temperature, and reaction time during the selenylation process. As the acetic acid concentration increased from 1% to 9%, the selenium content of the starches rose from 0.5 to 1.7 mg/g starch. This increase was accompanied by greater degradation and disorganization of the multi-scale structures of starch, which led to increased starch digestibility. In the gastrointestinal tract, selenylated starch released selenium in both oral and gastric phases, but most significantly in the small intestine. Notably, the selenium content of selenylated starch after the upper gastrointestinal digestion increased from 0.015 to 0.27 mg/g starch when the acetic acid concentration rose from 1% to 9%. These findings enhance our understanding of the structures and physicochemical properties of selenylated starch, providing insights for the development of health-promoting foods.