Phase transition induced bywater dilution in phospholipid U-type food-grade microemulsions studied by DSC

In this study we used differential scanning calorimetry to clarify the role of water activity within the nano-droplets, and to explore phase transitions in novel phospholipids based fully dilutable food-grade microemulsions. The microstructure transitions were investigated along two water dilution lines (50:50 and 80:20 mass% surfactant mixture/oil phase). From the water thermal behavior we learned that three structural regions can be identified along the water dilution lines. The thermal transition points coincide with the structural phase transition of the microemulsions as measured by other methods (electrical conductivity and SD-NMR measurements). The structural transitions were detected at 20 and 45 mass% of water along dilution line 55, where along dilution line 82 it occurs at 40 and 50 mass% of water. The microemulsions along dilution line 82 seem to have more compact surfactant packing film, thus the film has stronger resistance to transformation upon dilution, resulting in a smaller bicontinuous region than the one formed at dilution line 55. The difference in phase transition point can be used for triggering the release of future solubilizate.