Controlling crystallization processes of oil droplets in oil-in-water (O/W) emulsion droplets is a vital subject in emulsion technology employed in foods, cosmetics and pharmaceuticals. We performed visual observation, DSC analysis, synchrotron radiation microbeam X-ray diffraction (SR-μ-XRD) experiments on crystallization of palm-mid-fraction (PMF) in O/W emulsion droplets to elucidate fundamental mechanisms of crystallization phenomena in O/W emulsion droplets which are influenced by interfacial heterogeneous nucleation. The emulsification of PMF in water was done by using liquid-type emulsifiers, and we added high-melting emulsifies of hydrophobic (P-170) and hydrophilic (P-1670) sucrose fatty acid esters into the oil and water phases, respectively, so that these additives may act as templates for heterogeneous nucleation of PMF crystals. The crystallization temperature of PMF increased by adding P-170 additive and the crystal morphology also changed with the two types additives compared with non-additive emulsion droplets. The SR-μ-XRD experiments unveiled that the lamellar planes of PMF crystals near the outer edges of the additives-added emulsion droplet were mostly parallel to an oil-water interface, whereas the lamellar planes were randomly oriented to the interface in the pure emulsion droplets. From these results, we confirmed that the additives caused interfacial heterogeneous nucleation through hydrophobic interactions, which influenced the arrangements of fat crystals so that the lamellar planes of fat crystals were parallel to the oil-water interface. The stability of crystallized emulsions in chilled temperature can be controlled by interfacial heterogeneous crystallization which are promoted by the additives.

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Partial coalescence plays an important role in determining the quality of O/W type food emulsions. In this manuscript, factors relating to the partial coalescence such as solid fat contents, contact angle, concentrations of dispersed phase, size of oil droplet, etc., were reviewed. Based on our results, the mechanism whereby solid fats cause the partial coalescence of oil droplets was described. It was emphasized that the thermal change during the storage is of great importance for the partial coalescence. The effects of proteins and lecithins on the partial coalescence were also discussed from the viewpoints of final food products.

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Soft Matters such as polymer and lipid show spatially and temporally hierarchical structure, which results in the characteristic properties of soft matter. X-ray diffraction methods such as combined measurement of small- and wide-angle X-ray diffraction and microbeam X-ray diffraction are powerful tools to investigate such hierarchical structure. In this article, a brief introduction of these X-ray diffraction methods is described and an application of these techniques is presented to study crystallization of n-Hexadecane in oil-in-water emulsion.

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We succeeded in observing nano-nucleation by means of small angle X-ray scattering for the first time, which had been impossible to observe for about 80 years due to technical problems. We obtained size distribution f (N, t) of nano-nucleus and clarified the real-image of nano-nucleation. We also introduced "mass distribution function Q (N, t)" and proposed a new basic equation of the mass conservation law. This solved the serious problem in classical nucleation theory, where so called "fundamental kinetic equation" does not satisfy the mass conservation law. Polymer nucleation is the process of disentanglement and chain sliding diffusion along the chain axis due to the topological nature of chain-like polymers. We showed that nucleation and morphology changed under large elongational strain field: they discontinuously changed from heterogeneous to homogeneous ones and from spherulite to "nano-oriented crystals (NOC)", respectively, when the elongational strain rate increased larger than a critical elongational strain rate. Physical properties of the NOC were significantly improved.

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We have studied crystallization process of polymers under flows in a wide length scale from sub-nanometer to several tens micrometer using synchrotron radiation X-ray, neutron, depolarized laser light scattering and optical microscope. It was found that there exists a critical shear rate for the formation of the so-called shish-kebab structure which consists of extended chain crystal (shish) and folded chain lamella crystal (kebab), and the shish is formed from the high molecular weight component. It was also suggested that some oriented structure is formed in micrometer scale before the shish formation, which was assigned to a precursor of shish-kebab.

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Polymer crystallization is a very challenging subject in modern molecular simulations. We can directly visualize molecular processes of chain-folded crystallization at the crystal growth front, and also reveal intricate structures of highly supercooled melt and emerging crystallites having unprecedented morphologies. We here briefly survey our recent computer simulation studies of polymer crystallization, with special emphasis on the crystal growth and primary nucleation in simple polyethylene-like linear polymers.

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