Phase behavior of model lipid systems: Solubility of high-melting fats in low-melting fats

The solubility behavior of three high-melting fats (tripalmitin sample, PPP-S; cocoa butter-stearin, CB-S; and palm oil-stearin, PO-S) in five low-melting fats (tricaprylin, CCQ canola oil; sunflower oil; lard-olein, LD-O; and palm oil-olein, PO-O) was studied. To create the solubility curve, the high-melting fat was first equilibrated in the low-melting model lipid system between 25 and 62.5 degrees C for 1 wk. The amount of high-melting fat dissolved in the low-melting model lipid system was then determined by analyzing TAG compositions in the liquid phase using GC. The low-melting CCC formed partial solid solutions with each of the high-melting fats as a result of its very short chain length. PPP-S formed an ideal solution in all of the low-melting fats except CCC. The mixtures of CB-S/LD-O, CB-S/PO-O, and PO-S/LD-O deviated from ideality, illustrating closer interactions between TAG from CB-S and PO-S and those from LD-O or PO-O. The melting temperature and heat of fusion of the high-melting fats calculated from the Hildebrand equation was very close to those determined by DSC.