Fucoidan modification for stable melatonin O/W emulsions: Interfacial structure and properties

We investigated the effects of 2-Octen-1-ylsuccinic anhydride (OSA) modification and ultrasound on the structure, interface, and emulsification ability of fucoidans (FUCs). A modified polysaccharide emulsion system containing melatonin with high stability was established. The results demonstrated that the interfacial tension of the modified FUCs decrease gradually and the amphiphilicity was improved. The 9 %-OSA-FUCs emulsions ultrasonicated at 400 W presented the smallest volume-average droplet diameter (1.34 ± 0.03 μm) and the storage stability were also remarkably improved by the processing method. Meanwhile, the emulsion system enhances melatonin bioaccessability, effectively shielding it from the gastrointestinal environment and ensuring stable delivery to the small intestine for optimal absorption. At the same time, the emulsion system improves the bioaccessability of melatonin (55.32 % > 24.20 % of melatonin) and effectively delay the release of FFA in first 10 min (17.72 % < 21.98 %). This study provides insights into rational modification strategies for functional polysaccharide-based emulsifiers and designing delivery systems for chemically labile hydrophobic bioactive components.