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. 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. 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 were crystallized as the unstable polymorphs, the α or β’ forms first, and then they were transformed into β forms by solid–solid transformations. 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. The β forms obtained showed different melting points. Additional heat treatment promoted further polymorphic transformation. Four novel β forms were found for each of the saturated monoacid TAGs, trilaurin, trimyristin, tripalmitin, and tristearin. They showed similar polymorphism with the same subcell packing.

The crystallization behavior of the metastable $\alpha$ form of triacylglycerols (TAGs) plays a critical role as a precursor for the crystallization of more stable ${\beta }^{\prime }$ and $\beta$ forms for various applications in food and pharmaceutical products. However, precise analysis of the crystallization kinetics of $\alpha$ has not been performed, likely due to its rapid and complex behavior. This paper presents the observation results of the initial stages of the isothermal crystallization kinetics of $\alpha$ forms of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (rac-PPO), and molecular compound (MC) crystals of a POP/rac-PPO (1/1) mixture (MC${}_{\mathrm{POP}/\mathrm{PPO}}$) using synchrotron radiation time-resolved X-ray diffraction and polarized optical microscopy. In all the TAGs, $\alpha$ crystals with a worm-like morphology started to grow rapidly in the first stage. Then, the $\alpha$ crystals slowly transformed into more stable forms in different manners for different TAG samples. In POP, the conversion was simple, as the $\alpha$-2 form transformed into $\gamma$-3, whereas in rac-PPO, the lamellar distance values of the $\alpha$-2 form continuously decreased with time and changed into the $\alpha$-3 form. In the MC${}_{\mathrm{POP}/\mathrm{PPO}}$ crystals, in contrast, separate crystallization of $\alpha$-2 of a rac-PPO fraction initially occurred, followed by the crystallization of $\alpha$-2 of POP, and the two $\alpha$ forms merged into $\alpha$-2 of MC${}_{\mathrm{POP}/\mathrm{PPO}}$. This separate crystallization was caused by large differences in the crystallization kinetics of the $\alpha$ forms of POP and rac-PPO.

The polyol process is a straightforward method to produce metallic compounds through transformation from metal salt. An optimized procedure based on the polyol process in this research was developed for the selective synthesis of α-nickel hydroxide from metal salt. From various experimental results, the preparation of the sodium salt of ethylene glycol was crucial for the efficient production of α-nickel hydroxide. The structure of α-nickel hydroxide was studied by powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, transmission electron microscopy, and scanning electron microscope. The estimated Gibbs free energies for each step of the polyol process, employing density functional theory (DFT) calculations, confirmed the formation of nickel reaction intermediates, which mitigated the production of metallic nickel. The innovative point of this research is the finding that the intentional generation of nickel reaction intermediates leads to selective synthesis of α-nickel hydroxide.