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.

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African elephant milk fats from different stages of lactation are studied to investigate the link between high contents of medium-chain fatty acids (MCFA), triacylglycerol (TAG) species, and crystallization in a milk fat system. The elephant milk fats contain high amounts of MCFA, specifically C8:0, C10:0, and C12:0, which mainly form medium molecular weight TAG species (C26-C34). The milk fats with the highest MCFA levels (97% and 82%) correspond to mid-and late-lactation stages. These milk fats display simpler TAG compositions and crystallization behaviors. The great majority of midand late-lactation milk fats are comprised of medium molecular weight (C28-C30) TAG. Both melting and crystallization are sharp events, and only ' polymorph is observed. At early lactation, with 66% MCFA, a more diverse fatty acid composition is observed, and TAG species with medium molecular weight (C30-C34) and high molecular weight (C36-C44) are the dominant. Under dynamic conditions, crystallization and melting take place gradually over a wide temperature range, both and ' polymorph crystals are observed. Practical Applications: Mammals of different species provide milk lipids with a wide variety of fatty acid composition yet with common stereospecific features. The study of milk lipids, other than the common bovine milk lipids, allows the investigation of crystallographic properties in relation to fatty acid composition while preserving the stereospecific arrangement. Specifically, the study of elephant milk fats from different stages of lactation provides insight in to the effect of varying contents of medium-chain fatty acids and fatty acid diversity on triacylglycerol composition and crystallization behavior.

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The physical properties of milk fat are intrinsically related to its chemical composition. This in turn is linked to animal feeding and to a lesser extent to genetics. Understanding the relation between these factors is utmost important to define the effects of animal feeding strategies on milk fat and milk fat rich products. In the present chapter, an overview of high-throughput techniques useful in the study of milk fat triacylglycerols is given. The latest advances in the study of milk fat microstructure structure are summarized. Moreover, the relation between cow’s feeding regimes, milk fat composition and its crystallization microstructure is presented. Finally, we present two cases of study where chemical and physical techniques are used to understand the milk fat thermal behavior and microstructure.