Crystallization of model fat blends containing symmetric and asymmetric monounsaturated triacylglycerols

In this study, the crystallization and melting properties of four different fat blends with the same saturated fat content (30%) but with different ratios of symmetric and asymmetric monounsaturated triacylglycerols were investigated using pNMR, DSC and polarized light microscopy. Blends were either palmitic (P) or stearic (S) based, and were combinations of SatOSat-rich (Sat = saturated, O = oleic) and SatSatO-rich vegetable oils with high-oleic sunflower oil. The DSC results demonstrate that there was almost no difference in crystallization mechanism and crystallization rate between the two P-based blends. Both blends showed a two-step crystallization, which can be explained by polymorphism. Stop-and-return DSC results suggested an initial crystallization into an unstable polymorph followed by polymorphic transition during the crystallization. For the S-based blends there was a clear difference between the SOS-rich and the SSO-rich blend, with a slower crystallization for the SSO-rich blend. Possibly, this can be explained by fractional crystallization. The microstructure did not differ greatly between the blends. Directly after crystallization, the crystals of the SSO-rich blend were slightly larger than the crystals of the SOS-rich blend.