Phase diagrams of mixtures of n-hentriacontane and saturated monoacid triacylglycerols

Abstract

Gelation of vegetable oils with candelilla wax (CW) and saturated triacylglycerols (TAGs) is a promising strategy for engineering fat-based foods, cosmetics, and drug delivery systems. n-hentriacontane (C31) defines, to a large extent, the thermal properties of CW. Therefore, the phase behavior and microstructure of binary mixtures of C31 and trimyristin (MMM), tripalmitin (PPP), or tristearin (SSS) were studied to provide a better understanding of complex mixtures of CW and saturated fats. Phase diagrams were developed by differential scanning calorimetry and X-ray diffraction measurements. The mixtures showed a eutectic phase behavior, in which the C31-TAG mixtures below the solidus line were solid dispersions of crystals rich in C31 and crystals rich in the corresponding TAG. This segregation in the solid phase was attributed to the incompatible subcell-packing of the pure components in the stable polymorphic form, which was orthorhombic for C31, and monoclinic for TAGs in the β-polymorphic form. C31 had a major effect on TAGs microstructure. Morphological changes at the microstructural level were caused by the heterogeneous nucleation of MMM on C31 crystals. Conversely, microstructural changes for TAGs crystals in C31-PPP and C31-SSS mixtures were induced by the inhibition of crystal growth due to the transient adsorption of C31 molecules at the growing crystal surface.