On the optimisation of water droplet encapsulation within fat crystal shells

Novel means of water droplet encapsulation within solid matrices are sought for applications ranging from bioactive delivery to flavour and texture control. Model water-in-oil emulsions containing a 10 wt% dispersed aqueous phase were formulated using a continuous phase composed of soybean oil and hydrogenated soybean oil. Polyglycerol polyricinoleate and glycerol monooleate were incorporated in order to stabilize the emulsion. Encapsulation was achieved by applying controlled shear during cooling from 80 to 20 °C on a rheometer stage. Cooling rates of 0.5, 1.0, or 2.0 °C/min and shear rates of 500, 1000, or 2000 s -1 were investigated. Polarized light microscopy confirmed the formation of fat crystal shells encapsulating aqueous droplets under most conditions, with the exception of the highest shear (2000 s -1 ) combined with the slowest cooling rate (0.5 °C/min). Higher shear rates generally produced smaller water droplets and more spherical fat crystal shells whereas slower cooling rates promoted larger spheroidal shells and the occurrence of multi-droplet encapsulation. The fat phase exhibited varying β′/ β ratios depending on the shear-cooling conditions used. Overall, this study demonstrated that the morphology of water droplets encapsulated within crystalline fat shells can be tailored by controlling shear and cooling rates. • Confined gap shear-cooling allows water droplets to be encapsulated within fat crystal shells • A simultaneous action of cooling and shear is required for droplet encapsulation • Encapsulation is achieved via a two-step process: (i) emulsion formation and (ii) shear-cooling • Tuning shear-cooling conditions can maximise extent of encapsulation