Polymorphism of milk fat studied by differential scanning calorimetry and real-time X-ray powder diffraction

The crystallization behavior of milk fat was investigated by varying the co oling rate and by isothermal solidification at various temperatures while m onitoring the formation of crystals by differential scanning calorimetry (D SC) and X-ray powder diffraction (XRD). Three different polymorphic crystal forms were observed in milk fat: gamma, alpha, and beta'. The beta-form, o ccasionally observed in previous studies, was not found. The kind of polymo rph formed during crystallization of milk fat from its melted state was dep endent on the cooling rate and the final temperature. Moreover, transitions between the different polymorphic forms were shown to occur upon storing o r heating the milk fat. The characteristic DSC heating curve of milk fat is interpreted on the basis of the XRD measurements, and appears to be a comb ined effect of selective crystallization of triglycerides and polymorphism.