Nucleation Kinetics during Melt Crystallization of Plant Based High Oleic and Linoleic Polyunsaturated Fatty Acid Mixtures

Nucleation kinetics of high linoleic and high oleic polyunsaturated fatty acid (PUFA) mixtures were investigated during melt crystallization by means of a focused beam reflectance measurement (FBRM) sensor. Samples were analyzed thermally and chemically in the differential scanning calorimeter (DSC) and gas chromatograph (GC), respectively. Investigations showed that a high oleic content in the PUFA mixtures lead to higher induction times, τi. Unlike previous investigations, a clear relation between τi and cooling rates was established: τi increases with increasing cooling rates and decreasing supercooling. Activation energies of nucleation, ΔGc′, were determined by means of the Fisher Turnbull equation wherein ΔGc′ decreases exponentially with increasing supercooling. Investigations and further evaluations conclude that while the plot establishes the effect of supercooling on ΔGc′, it does not incorporate the effects of molecular diffusion or the cooling rate. Hence, 3D modeling was performed to visualize the combined effects of cooling rate and supercooling on induction time.