Polymorphic Effects of Adding Anhydrous Milk Fat to the High-Melting Fraction of Extra Virgin Olive Oil

We studied the polymorphic crystallization and transformation behavior of mixtures of the high melting fraction (HMF) of extra virgin olive oil (EVOO) and anhydrous milk fat (AMF). Samples were prepared at every 10% concentration ratio, and their thermal behavior was analyzed when cooled from the melt (50 °C) to complete crystallization (−50 °C) and reheated to the melt at a controlled rate of 2 °C/min. Time-resolved synchrotron X-ray diffraction (SR-XRD), based on simultaneous small- (SR-SAXD) and wide- (SR-WAXD) angle measurements, allowed the polymorphic identification of selected samples of the HMF of EVOO, AMF, and mixtures of 30AMF/70HMF, 50AMF/50HMF, and 70AMF/30HMF. Both AMF and the HMF of EVOO exhibited six different polymorphic forms, being α or β′ subcell structures arranged in double or triple chain layered structures, the structural similarities of which significantly hindered the polymorphic distinction. The addition of AMF to the HMF of EVOO caused a significant increase in the crystallization and melting temperatures of the samples, owing to the occurrence of specific polymorphs of AMF. The mixtures exhibited immiscible behavior due to large differences in the saturated/unsaturated nature but also in chain length of the fatty acid moieties of AMF and HMF. The results presented in this work may mean another approach in the development of monounsaturated-rich soft fats with reduced saturated contents.