Simultaneous synchrotron radiation X‐ray diffraction‐DSC analysis of melting and crystallization behavior of trilauroylglycerol in nanoparticles of oil‐in‐water emulsion

Crystallization, polymorphic transformation, and melting behavior of nanoparticles of trilauroylglycerol (LLL) in oil‐in‐water (O/W) emulsion were examined initially by DSC, and then by simultaneous synchrotron radiation small‐angle (SAXS) and wide‐angle (WAXS) X‐ray diffraction and DSC (SR‐SAXS /WAXS/DSC). The O/W nanoparticles emulsions having average diameters of 42 to 120 nm were prepared by application of mechanical shear using a high‐pressure homogenizer. The following results were obtained: (i) The DSC study showed that the melting temperature of the stable β form of LLL was reduced from 46.7 (bulk) to 26.5–44.0°C (nanoparticles); this variation as assumed to be due to the size distribution of the nanoparticles. Crystallization temperature was also reduced from 18.9 (bulk) to −9.5±0.5°C (nanoparticles). These results were consistent with those of previous studies of nanoparticles of fats obtained in the O/W emulsion. (ii) The results obtained by the SR‐SAXS/WAXS/DSC technique during the cooling process to −20°C showed that the first‐occurring polymorph of LLL in the bulk liquid was β′, whereas α was first nucleated and transformed to β′ around −10°C during cooling in the nanoparticles. (iii) The SR‐SAXS/WAXS/DSC data taken during the heating process from −20°C after the crystallization showed that β′ transformed to β around 0°C and that the melting of β started at 30°C and ended at 44°C. The present study showed that forming nanoparticles of LLL in the O/W emulsion having the diameters of 42 to 120 nm reduced the melting and crystallization temperatures and increased the transformation rate of α→β′→β in comparison to the LLL crystals formed in the bulk phase.