Boodhoo Marc V, Bouzidi Laziz, Narine Suresh S
Alberta Lipid Utilization Program, Department of Agricultural Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada.
Chem Phys Lipids. 2009 Jan;157(1):21-39. doi: 10.1016/j.chemphyslip.2008.08.002. Epub 2008 Sep 4.
The phase behavior of a binary system constituted of purified 1,3-dicaproyl-2-stearoyl-sn-glycerol (CSC) and 1,2-dicaproyl-3-stearoyl-sn-glycerol (CCS) was investigated at a very slow (0.1 degrees C/min) and a relatively fast (3.0 degrees C/min) cooling rate using differential scanning calorimetry (DSC), low resolution NMR, X-ray diffraction (XRD), and polarized light microscopy (PLM). Related forms of the beta' polymorph were detected for all mixtures as well as a beta form for CSC-rich mixtures. A double chain length (DCL) stacking of the non-mixed CCS-CCS and CSC-CSC phases and a triple chain length (TCL) stacking of mixed CCS-CSC structure were detected for the different beta' forms. The kinetic phase diagram demonstrated an apparent eutectic at the 0.5(CSC) composition when cooled at 0.1 degrees C/min and at the 0.25(CSC) composition when cooled at 3.0 degrees C/min. The application of a thermodynamic model based on the Hildebrand equation suggests that compounds CSC and CCS are not fully miscible. In addition, the miscibility changes according to the structure of the growing solid phase which is dependent on CSC molar ratio as well as on the kinetics. It was also shown that the miscibility is concentration dependent and that the solid phase, which is growing at conditions well away from equilibrium, is determined kinetically. The molecular interactions were found to be strong and to favor the formation of CSC-CCS pairs in the liquid state. CSC and CCS were also shown to be immiscible in the solid state. Depressions in solid fat content (SFC) were observed for both rates. Relatively complex networks made of needle-like, spherulitic and granular crystals were observed in the CSC/CCS system. A pure CSC phase was found to be instrumental in promoting a higher SFC, and more stable polymorphic forms. The microstructure was shown to be strongly dependent on the cooling rate and was linked to the different polymorphic forms observed by DSC and XRD. Correlations between SFC and the eutectic behavior have been observed for the 3.0 degrees C/min cooling rate, but not directly in the case of the 0.1 degrees C/min cooling rate, where slower kinetics which favors the metastable to stable phase conversion processes prevented the same shifts in behavior.
使用差示扫描量热法（DSC）、低分辨率核磁共振（NMR）、X射线衍射（XRD）和偏光显微镜（PLM），在非常缓慢（0.1℃/分钟）和相对快速（3.0℃/分钟）的冷却速率下，研究了由纯化的1,3 - 二己酰基 - 2 - 硬脂酰 - sn - 甘油（CSC）和1,2 - 二己酰基 - 3 - 硬脂酰 - sn - 甘油（CCS）组成的二元体系的相行为。在所有混合物中均检测到β'多晶型的相关形式，以及富含CSC的混合物中的β形式。对于不同的β'形式，检测到未混合的CCS - CCS和CSC - CSC相的双链长度（DCL）堆积以及混合的CCS - CSC结构的三链长度（TCL）堆积。动力学相图表明，在以0.1℃/分钟冷却时，在0.5（CSC）组成处出现明显的共晶点；在以3.0℃/分钟冷却时，在0.25（CSC）组成处出现明显的共晶点。基于希尔德布兰德方程应用的热力学模型表明，化合物CSC和CCS并非完全互溶。此外，表示根据生长的固相结构的互溶性变化，这取决于CSC摩尔比以及动力学。还表明互溶性取决于浓度，并且在远离平衡条件下生长的固相是由动力学决定的。发现分子间相互作用很强，并且有利于在液态中形成CSC - CCS对。CSC和CCS在固态下也表现为不互溶。两种冷却速率下均观察到固体脂肪含量（SFC）降低。在CSC/CCS体系中观察到由针状、球晶状和粒状晶体组成的相对复杂的网络。发现纯CSC相有助于提高SFC，并形成更稳定的多晶型形式。微观结构显示出强烈依赖于冷却速率，并且与通过DSC和XRD观察到的不同多晶型形式相关。对于3.0℃/分钟的冷却速率，观察到SFC与共晶行为之间的相关性，但在0.1℃/分钟冷却速率的情况下未直接观察到，较慢的动力学有利于亚稳到稳定的相转变过程，阻止了相同的行为变化。
