Droplet-stabilized oil-in-water emulsions protect unsaturated lipids from oxidation.

Droplet-stabilized emulsions use fine protein-coated lipid droplets - the shell - to emulsify larger droplets of a second lipid - the core. This study investigated the oxidation resistance of polyunsaturated fatty acid oil (PUFA oil) within droplet-stabilised emulsions, using shell lipids with a range of melting points: olive oil (low melting), trimyristin (high-melting) and palmolein oil (intermediate melting point). Oxidation of PUFA oil was accelerated with a fluorescent lamp in the presence of ferrous iron (100 μM) for nine days, and PUFA oxidation was monitored via conjugated dienes, lipid hydroperoxides and hexanal levels. Oxidation was slower in droplet-stabilized emulsions than in conventional emulsions or control emulsions of the same composition as droplet-stabilized emulsions but different structure, and trimyristin gave the greatest oxidation resistance. Results suggest the structured interface of droplet-stabilized emulsions limits contact between pro-oxidants and oxidation-sensitive bioactives encapsulated within, and this anti-oxidative effect is greatly enhanced with solid surface lipid.