Lipase-catalyzed synthesis of antibacterial and antioxidative erythorbyl ricinoleate with high emulsifying activity.

Erythorbyl ricinoleate (ERO) was synthesized as a novel multi-functional emulsifier with antibacterial and antioxidative activities via lipase-catalyzed esterification between erythorbic acid and ricinoleic acid. Esterification regioselectively produced ERO (6-O-ricinoleoyl-erythorbate) of 238.67 mM at 48 h. ERO effectively reduced interfacial tension to 2.66 mN/m at its critical micelle concentration (0.73 mM), compared with other erythorbyl fatty acid esters (EFEs). Oil-in-water (O/W) emulsion stabilized by ERO remained stable for 15 days with a droplet size of 256.3 nm and polydispersity index of 0.22, whereas the emulsion stabilized by the other EFEs became unstable within six days. ERO had antibacterial activity against Gram-positive bacteria with minimum inhibitory concentrations from 0.2 to 0.6 mM. In O/W emulsion, ERO exhibited higher antioxidative activity than erythorbic acid against lipid oxidation. These findings suggest that ERO has high potential as multi-functional food additive to control lipid oxidation and bacterial contamination for O/W emulsion foods.