Preparation, structural characterization and microencapsulation of antioxidant peptides from selenium-enriched millet

Selenium (Se)-enriched protein is the main form of Se in Se-enriched millet and has strong biological activity. In order to explore the high-value utilization of Se-enriched millet protein (SMP), this study first optimized the extraction process of SMP and determined its antioxidant activity. Alkaline protease was identified as the most suitable enzyme, and the optimal hydrolysis process was pH 10, temperature 45 ℃, time 4 h, enzyme dosage 5%. Under these conditions, the antioxidant activity of SMP hydrolysate was evaluated. The ABTS free radical scavenging rate, DPPH free radical scavenging rate and hydroxyl free radical scavenging rate reached 69.77%, 79.01% and 77.91%, respectively. The enzymatic hydrolysis solution exhibited antioxidant activity, showing a good dose-effect relationship. Then, the antioxidant activities of Se-enriched millet antioxidant peptide (SMAP) and common millet antioxidant peptide (MAP) were evaluated. The antioxidant activities of two protein peptide ultrafiltration components (SMAP I: 3 kDa < Mw < 10 kDa, SMAP II: < 3 kDa) were purified, and 6 peptides with high antioxidant activity were identified. The results showed that the antioxidant activity of SMAP II was better. The Se content and antioxidant activity of SMAP were higher than those of MAP, and the antioxidant activity of SMAP was similar to that of Vc. Finally, sodium alginate was selected as the wall material, and the purified product was microencapsulated and verified by in vitro experiments. The study may provide a theoretical basis for the preparation and practical application of Se-enriched proteins and antioxidant peptides.