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Effect of weighting agent and high pressure homogenization on stability of water-in-oil-in-water double emulsion
The purpose of this research was to investigate the effect of weighting agent (WA) and high pressure homogenization (HPH) on the stability of water-in-oil-in-water double emulsion (DE). To prepare oil phase (O), olive oil, glycerol ester of wood rosin (WA; variable 1), and polyglycerol polyricinoleate (lipophilic emulsifier), and for interior water phase (W1), deionized water, gelatin, sodium chloride, ascorbic acid, and green tea extract(core material) were mixed and heated. When temperature of O and W1 reached up to 60℃, W1 was dispersed into O dropwisely followed by magnetic stirring at 1500 rpm for 2 min (O:W1=3:1). By applying homogenization at 4000 rpm for 2 min followed by ultrasonication for 4 min, water-in-oil primary emulsion (PE) was produced. And resting PE at 4℃ for 30 min was followed. For exterior water phase (W2), deionized water, sodium chloride, ascorbic acid, and polysorbate 80 (hydrophilic emulsifier) were mixed. When temperature of PE reached at room temperature (24 ± 2℃), PE was dispersed into W2 dropwisely followed by magnetic stirring at 1500 rpm for 15 min (PE:W2=1:3). By applying ultrasonication for 2 min followed by HPH at 500 bar for 1 to 3 times (variable 2), DE was produced. When DE was freshly produced, phase separation occurred at different period of time depending on whether variable 1 and 2 were applied or not (from 5 min to more than a day). The structure of DE was observed through optical and transmission electron microscopy. And relationship between the mean size of oil droplets and the occurring time of phase separation was studied. DE can be used as an appropriate delivery system for co-loading both hydrophilic and lipophilic bioactive compounds simultaneously, and promoting industrialization as well by applying it to food products, for example, beverage.
