Fat crystallization and melting in W/O/W double emulsions: Comparison between bulk and emulsified state

Water-in-oil-in-water (W/O/W) technology enables the development of an emulsion-based delivery system for functional food applications. The functionality of this system depends on the oil barrier of the double emulsion, whereby the fat matrix properties (e.g. solid fat content) play an important role. First, the effect of W/O/W emulsification on fat crystallization and melting behavior was studied and compared to bulk fat. Second, the effect of fat composition was investigated. As such, W/O/W emulsions were produced with a slow and fast crystallizing fat, i.e. soft palm mid fraction (sPMF) and partially hydrogenated sunflower oil, respectively, upon cooling and subsequent isothermal crystallization. Low resolution NMR and DSC techniques were applied, and indications about the polymorphic behavior were verified by real-time synchrotron XRD measurements. Except from increased supercooling, the overall fat crystallization dynamics in the W/O/W emulsions were similar to bulk, irrespective of the used fat. Yet, broadening of the long spacing peaks in the W/O/W emulsions indicated less ordered triacylglycerol longitudinal stacking compared to bulk. This effect was more pronounced in case of alpha-crystals than beta'-crystals. With respect to W/O/W functionality, the melting behavior of the W/O/W-sPMF emulsion showed promise as a possible carrier system with a thermo-responsive release mechanism for functional foods.