Observations on the influence of different biopolymers on coalescence of inner water droplets in W/O/W (water-in-oil-in-water) double emulsions

The use of biopolymers as hydrophilic emulsifiers in water-in-oil-in-water double emulsions is often proposed in literature [1,2]. They are supposed to not diffuse from one water phase into the other one and thus being better suitable for the stabilization of W/O/W emulsions than short-chain hydrophilic emulsifiers. We compare different biopolymers as emulsifiers and stabilizers for food grade W/O/W emulsions. Egg yolk and whey protein isolate (WPI) were used as typical emulsifiers in foods. Pectin, gum arabic and carboxy methylcellulose (CMC) were chosen as typical food stabilizers. For comparability, we produced double emulsions of different oil drop size. Encapsulation efficiency was measured by a DSC method that allows for direct determination of the amount of encapsulated water. The relationship between encapsulation efficiency and oil drop size was independent of emulsifier concentration when using egg yolk. In contrary, the encapsulation efficiency of WPI-stabilized emulsions decreased with increasing concentration. Moreover, a stabilization of W/O/W emulsions is possible by exclusively using selected stabilizers in the outer water phase. Highest encapsulation efficiencies were found for CMC-stabilized double emulsions. Measurement of interfacial tensions revealed that this stabilizer has the lowest interfacial activity. These results indicate that using a biopolymer does not guarantee for double emulsion stability. (C) 2014 Elsevier B.V. All rights reserved.