Mixing phase behavior of trilaurin and monounsaturated triacylglycerols based on palmitic and oleic fatty acids

Differential scanning calorimetry and X-ray diffraction were used to examine the mixing phase behavior of LLL (trilaurin or 1,2,3-trilauroyl-glycerol) and POP (1,3-dipalmitoyl-2-oleoyl-glycerol), PPO (1,2-dipalmitoyl-3-oleoyl-rac-glycerol), or the 50POP/50PPO blend able to form a molecular compound. This research aims to provide an insight into the molecular interactions ruling the physical behavior of fat blends of lauric (i.e., coconut oil) and non-lauric lipids (cocoa butter, palm oil, etc.). The results showed eutectic behavior and no mutual solubility of triacylglycerols in stable LLL/POP and LLL/PPO mixtures. Applying high-rate cooling treatments had a positive effect on miscibility, but the high incompatibility of the components due to differences in length and degree of unsaturation of fatty acids was still evident in metastable polymorphs. In ternary LLL/(50POP/50PPO) mixtures, on the other hand, molecular compound β-2L crystals formed by POP and PPO showed to favor the solubility of LLL as compared to the binary systems. Accordingly, promoting the presence of triacylglycerols forming molecular compound in specific fat blends may help reducing eutectic or incompatible interactions among triacylglycerol molecules in the solid state. These lead to phase separation and are a major cause of the restricted applicability of lauric oils in the confectionery and chocolate industries.