Phase behavior of triolein and tripalmitin detected by differential scanning calorimetry

Abstract

The thermotropic behavior of triolein, tripalmitin and their mixtues was determined by differential scanning calorimetry. Polymorphic behavior was noted for the triglycerides but the triglycerides were converted to a single form after 4 to 5 successive heating scans. Melting points for each triglyceride were determined for the pure samples and mixtures, and plotted as a phase diagram. The phase diagrams indicate that a phase separation of triglycerides occurred at all concentrations of triolein and tripalmitin. However, the melting peak onset temperature of tripalmitin was shifted by triolein from 56 C at 100 mol % tripalmitin to 37 C at 15 mol % tripalmitin. Similarly, the peak onset temperature of triolein was shifted by tripalmitin from −2.5 C at 100% triolein to −4 C at 95% triolein. Enthalpies were also determined for pure samples and mixtures. These data indicated that when either triolein or tripalmitin were present as the minor component of the mixture, the enthalpy of the minor component was reduced whereas that of the major component was not greatly altered.