Synthesis and Characterization of Chitosan Oligosaccharide Selenium Nanoparticles and Selenium Enrichment Evaluation and Mechanism on Soybean Sprouts

Biofortification is an effective way to increase micronutrient levels in food crops. This study investigated selenium enrichment as a biofortification strategy in soybean sprouts. Chitosan oligosaccharide selenium nanoparticles (COS-Se NPs) were synthesized and used in soybean sprout culture to study their effects on the sprouts. The results showed that the enrichment factor value (EF) was higher when the concentration was 2.36–9.43 mg·L–1 compared with other concentrations, and the enrichment factor (EF) reached a maximum value of 0.9782 at a COS-Se NP concentration of 4.72 mg·L–1. Translocation factors (TFradicle-hypocotyl and TFhypocotyl-cotyledon) reached maximum values of 0.7866 and 0.9723 at 25.15 mg·L–1 and 15.09 mg·L–1, respectively, suggesting the relationship between enrichment of nanoselenium and concentration was not proportional. Most of the organic selenium was present mainly in the protein fraction, and albumin and glutelin were the main protein-bound seleniums. The contents of protein and biomacromolecule selenium reached higher values at a COS-Se NP concentration of 2.36–9.43 mg·L–1. Furthermore, the COS-Se NPs at 2.36–9.43 mg·L–1 concentration significantly affected the nutrient parameters in soybean sprouts. Different concentrations of COS-Se NPs were observed to have different effects on the mineral element content of the bean sprouts. In vitro digestion and dialysis experiments showed that the bioavailability of K, Mg, P, and Se was at a high level, while that of Fe and Ca was at a low level in soybean sprouts. Overall, no significant impact on the bioaccessibility of most elements was observed during the enrichment process compared to the control group. This work shows that the selenium enrichment strategy can be a potential soybean sprout production method and help solve the problem of nutritional deficiencies with selenium and reduce malnutrition.