Investigation of the Crystallization and Melting of the Tripalmitin/Triolein System via Hot Stage Microscopy, Differential Scanning Calorimetry, and Pulsed NMR

The isothermal crystallization kinetics and melting behavior of mixtures of tripalmitin (PPP) and trioleio (OOO) were investigated' using hot stage microscopy (HSM), with supporting differential scanning caloritnetry (DSC) and NMR measurements. Some melting points determined via HSM and DSC were higher than predicted by the Hildebrand equation, but solid fat content melting profiles from NMR were dose to ideal predictions. The observed deviations from ideal behavior with HSM/DSC could be attributed to concentration gradients in the liquid phase, rather than from nonideality. Sufficient time should therefore be allowed in melting experiments for diffusional equilibration to occur the remelting time should generally be longer than the crystallization time. When crystallizing mixed PPP/OOO samples, two distinct polymorphs could be seen in the same "crystal", With an outer ring of beta' surrounding an:inner circle of beta. Polymorphic transformation from beta' to beta could be seen to occur-via dissolution through a narrow liquid interface region between the two crystals. Growth rate data for were proportional-to the reduced saturation (or supercooling) calculated assuming' deal behavior. Growth rates of beta via the solvent/melt mediated:transformation of the beta' form could be related to driving forces based on the difference in solubility of the beta' and beta forms.