Investigating the effect of composition on the polymorphic pathways in mixtures of trisaturated and mono-unsaturated triglycerides and its translation into commercial blends

In this contribution, the crystallization kinetics of model fat blends containing trisaturated (H3) and mono-unsaturated (H2U) triglycerides (TAGs) are investigated via differential scanning calorimetry (DSC) and time-resolved short and wide-angle X-ray scattering (SAXS/WAXS). The composition of the H3 and H2U TAGs (stearic versus palmitic sources) and the cooling rate (1 versus 10 K min^-1) were varied to investigate the effect of composition on the mixed crystal formation and polymorphic pathways. Further, different events observed are linked to the crystallization kinetics of commercial blends, containing also medium-chain saturated fatty acids (M – constituting H2M TAGs). Under quiescent conditions, the blends revealed a multiple-step crystallization with co-existing polymorphic forms. Generally, H2U triglycerides tended to impede the polymorphic transition of the H3 fraction. H3 was found to act as a seeding agent in H2U crystallization with the polymorphic pathway of the latter determined by the applied cooling rate. In stearic-based blends, the transition into the most stable polymorphic form β was hindered when a fast cooling rate was applied. The introduction of H2M triglycerides – typically included in commercial blends – changed the crystallization pathways substantially by affecting the mixed crystal formation with H3 and H2U TAGs. Combining DSC and time-resolved SAXS/WAXS allowed assigning a dominant fraction to observed kinetic events. This way, the molecular makeup of the H3 and H2U fractions could be related to the kinetic pathways. This research offers a step towards understanding crystallization pathways in complex blends of commercial use which can be linked to clean model systems of similar molecular makeup.