Quantitative Phase Analysis of Complex Fats during Crystallization

The quantitative study of polymorphism in fats is complicated due to their complex composition and consequent intricate crystallization behavior. We aimed to illustrate how quantitative phase analysis can be performed in crystallizing complex fats. The advantages of our proposed method are that detailed structural information or internal standards are not needed and that it can be applied even to wide-angle X-ray diffraction patterns with a high noncrystalline (liquid fat) contribution and overlapping peaks. Diffraction patterns of palm oil and anhydrous milk fat during crystallization were decomposed by fitting a model based on Pearson type VII functions. From the decomposed patterns, the contribution of each phase was quantified as a function of time. Each contribution to the pattern was then converted to its mass fraction using response factors derived from the corresponding solid fat content, which was measured using low-resolution nuclear magnetic resonance (NMR). This approach allowed us to quantify the evolution of liquid and polymorphic phases during the early crystallization of complex fats and, for the first time, to quantify coexisting α, β′, and β phases. This method is flexible enough for fats with diverse triacylglycerol profiles yet detailed enough to quantify phase transitions in a system as complex as milk fat.