Multiple water-in-oil-in-water (W/O/W) emulsions are complex multiphase systems that consist of a water-in-oil emulsion dispersed in a continuous water phase. There is a great interest in the production of multiple W/O/W emulsions for different applications ranging from encapsulation of sensitive molecules for food, cosmetic and pharmaceutical products to fat reduction in food. For these applications, the encapsulation of internal water droplets or active agents in these droplets is crucial.
Water and/or active molecules encapsulated in the inner water droplets of W/O/W emulsions can be released into the outer water phase during production, storage and digestion of the emulsions. This release can either be caused by diffusion processes or by coalescence of inner droplets with the outer water phase.
In order to investigate water release by coalescence during the processing of W/O/W emulsions, we conducted single droplet experiments in a 4-roll mill as well as emulsification experiments. The release of water was quantified using a direct measurement technique based on differential scanning calorimetry (DSC). We found that coalescence can be observed independent from droplet deformation or breakup. Moreover, the emulsification experiments showed a direct correlation between encapsulation efficiency and oil droplet size. This correlation was strongly influenced by the dispersed phase content of the inner emulsion.
Release of anthocyanins encapsulated as active molecules in W/O/W emulsions during storage was investigated. It was found that the surfactant system in the outer water phase is a major parameter influencing release during production and digestion, however no influence was found on time dependent release during storage. Depending on the surfactant used, multiple emulsion droplets are able to survive stomach conditions. Intestinal conditions trigger the release of inner droplets, and thus their activity.
Mrs. Anna Schuch anna.schuch@kit.edu
