Abstract: The effects of the aliphatic chain length of polyglycerol fatty acid esters (PGFEs) on physicochemical characteristics, storage stability, antioxidant activity and antimicrobial activity of curcumin-loaded nanoemulsions were evaluated. It turned out that longer aliphatic chain of PGFEs increased the droplet size and decreased the zeta potential of nanoemulsions, but had little impact on the encapsulation efficiency of curcumin. Moreover, PGFE-stabilized nanoemulsions were stable for 28 days at 4 or 30 ℃, while the particle size of nanoemulsions drastically increased over time at 50 ℃, accompanied by rapid degradation of curcumin. Compared to other PGFEs, nanoemulsions formulated with polyglycerol capric acid esters (PGC) displayed greater thermal stability. Nanoemulsions stabilized by medium-chain PGFEs significantly (P < 0.05) enhanced the radical-scavenging activity of curcumin, and showed antimicrobial activity against Staphylococcus aureus and Escherichia coli. There was a synergistic inhibitory effect between PGFEs and curcumin.

Key words: polyglycerol fatty acid esters; curcumin; nanoemulsion; stability; antioxidant activity; antimicrobial activity