Monoglyceride self-assembled structure in O/W emulsion: formation, characterization and its effect on emulsion properties

Monoglycerides (MGs) can form self-assembled structures (liquid crystals) in aqueous or oil systems, which can structure emulsions. In this study, MG was incorporated in Tween 20 or whey protein isolate (WPI) stabilized O/W emulsions, and the crystallizing behavior of MG in the emulsions and its effect on emulsion properties were investigated. Differential scanning calorimetry (DSC) analysis indicated that in TW emulsions MG crystals were mainly in β form when stored at 25 °C, but in α and sub-α forms at 4 °C before finally transferred to β form. In WPI emulsions, only β-form MG crystals were formed regardless of the storage temperature. Synchrotron X-ray diffraction (XRD) study revealed that MG liquid crystals (β form) were stacking in a well ordered lamellar style with a bilayer thickness of 49.5 Å. α and sub-α forms of the crystals were packing in hexagonal and orthorhombic styles, respectively. MG structured WPI emulsions were unstable when subjected to lower pH or NaCl solutions, probably because of WPI replacement by MG, as well as the interaction between MG and WPI.