Formulation and characterization of monodisperse O/W emulsions encapsulating astaxanthin extracts using microchannel emulsification: insights of formulation and stability evaluation

The study used straight-through microchannel emulsification (MCE) to encapsulate different extracts of astaxanthin (AXT) in oil-in-water (O/W) emulsion droplets. We used silicon microchannel plates (WMS 11-1) containing 13,752 discrete 10×104μm microslots, connected to a circular microhole with a diameter of 10μm. Two different AXT extracts (AstaReal (AR) and Zenthin(®) (ZR)) based upon concentration and without purification was used as encapsulants in the dispersed phase, while different emulsifiers (1% (w/w) SDS, ML-750, MO-7S, Na-Cs and ML) with different stabilizing mechanisms were used as the continuous phase. The MCE was conducted at a dispersed phase flow rate of 1mLh(-1). Successful emulsification was conducted with a Sauter mean diameter of 35-37μm and relative span factor <0.25. The emulsification was highly depended on the type of emulsifiers and the extract type used during emulsification. Better droplet productivity was achieved with AR extract with 1% (w/w) ML-750 as the optimized emulsifier in Milli-Q Water. The O/W emulsion droplets remained stable at 25°C with encapsulation efficiency of over 98% during 15days of storage period.