Effects of Sodium Selenite on Accumulations of Selenium and GABA, Phenolic Profiles, and Antioxidant Activity of Foxtail Millet During Germination

This study investigated the influence of soaking and spraying with a sodium selenite (Na₂SeO₃) solution on selenium accumulation, γ-aminobutyric acid (GABA) content, phenolic compositions, and the antioxidant activity of foxtail millet sprouts. The screening results showed that foxtail millet seeds soaked with 60 mg/L of Na₂SeO₃ solution and sprayed with 2 mg/L of Na₂SeO₃ solution were the appropriate concentrations for the germination process. Compared with the spraying method, a presoaking treatment presented far higher selenium content and significantly higher (<i>p</i> < 0.05) selenium enrichment rates in foxtail millet sprouts. The content of free and bound phenolics, as well as GABA, were significantly (<i>p</i> < 0.05) increased in foxtail millet sprouts through both soaking and spraying treatments. Correspondingly, most of the individual phenolic compounds were significantly (<i>p</i> < 0.05) increased, especially after germination for 3 days. <i>Trans</i>-ferulic acid and <i>trans</i>-<i>p</i>-coumaric acid were the predominate bound phenolic acids, feruloylquinic acid and 4-<i>p</i>-coumaroylquinic acid were the major free-form phenolic compounds, and <i>N</i>-feruloyl serotonin and <i>N</i>-(<i>p</i>-coumaroyl) serotonin were the new arising phenolic derivatives caused by germination. Both the soaking and spraying treatments induced the enrichment of these individual phenolic compositions, thus increasing the total phenolic content and in vitro antioxidant activity of foxtail millet sprouts. It was indicated that selenium-enriched germination treatment should be an effective method to produce functional selenium-enriched foxtail millet sprouts with more abundant GABA and polyphenols, thus enhancing the health benefits and added value of foxtail millet.