This packing is characterized by a “subcell”, which is defined as the type of cross-sectional packing of aliphatic chains. Three typical polymorphs are well characterized based on the crystal packing of fatty acid moieties β, β’, and α in the order of the melting point. TAG crystals are well known to show polymorphism and monotropic transformations depending on the crystallization temperature, cooling rate, and storage temperature. Triacylglycerol (TAG), an ester of three fatty acids and glycerol, is the main constituent of fats and oils. They showed similar polymorphism with the same subcell packing. Four novel β forms were found for each of the saturated monoacid TAGs, trilaurin, trimyristin, tripalmitin, and tristearin. Additional heat treatment promoted further polymorphic transformation. The β forms obtained showed different melting points. The β form that had transformed from β’ changed its morphology by a polymorphic transformation, while the β form made from the α form kept its spherulite morphology. Saturated monoacid TAGs were crystallized as the unstable polymorphs, the α or β’ forms first, and then they were transformed into β forms by solid–solid transformations. In this study, we characterized a set of novel polymorphs, β forms of saturated monoacid TAGs, which were obtained via different pathways depending on the crystallization history, by polarized light microscopy, X-ray diffraction, and differential scanning calorimetry. Saturated monoacid TAGs, like trilaurin, are considered as models for TAG crystallization however, there is still debate about the number of their polymorphs that exist. We have investigated the polymorphism of triacylglycerol (TAG) crystals as they affect the qualities such as shelf life, mouth feel, and texture of chocolate and other products.

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