Solid phase behavior of mixture systems based on tripalmitoyl glycerol and monounsaturated triacylglycerols forming a molecular compound

Abstract

Differential scanning calorimetry and X-ray diffraction were used to investigate the mixing behavior of triacylglycerol (TAG) mixtures of PPP/PPO (tripalmitoyl glycerol/1,2-dipalmitoyl-3-oleoyl-rac-glycerol) and PPP/MC_POP/PPO (where MC_POP/PPO is the equimolecular blend of 1,3-dipalmitoyl-2-oleoyl-glycerol and PPO forming a molecular compound) under metastable and stable conditions. During cooling and reheating treatments at moderate rates, the eutectic properties of the two systems examined were mainly governed by the crystallization, transformation, and melting behavior of structurally similar β′ forms. In addition, steric and kinetic effects determined the formation of solid solutions with up to 10% and 20% of mixed-acid components in PPP/PPO and PPP/MC_POP/PPO mixtures, respectively. These values increased to 30% and 35% when thermodynamically stable β crystalline phases were obtained. In PPP/MC_POP/PPO mixtures, the diffraction data suggested that POP and PPO acted as a single component by dissolving in similar amounts in the solid solution phases and forming molecular compound crystals in eutectic compositions. This fundamental research shows the important role of specific combinations of mixed-acid TAGs and their interaction with high-melting components on the solidification behavior of edible lipids.