Crystallization of Mono- and Tripalmitin at the Air/MCT oil surface

Abstract

Glycerides such as mono- and triglycerides are present in nature and are involved in physiological processes such as lipolysis, emulsification and micellar transport. Crystalline glycerides were shown to stabilize air in oil dispersions which are denoted lipid or non-aqueous foams. This study investigates the influence of molecular structure, crystal polymorphic form as well as crystal morphology on the interfacial rheology of glycerides at the air/oil interface. In order to separate bulk and interfacial effects, 1 molar solutions of the respective glyceride in MCT-oil were prepared. The onset temperature of crystallization Tcryst onset as well as the enthalpy of crystallization ΔHc was measured by nano DSC. Crystal polymorphic form was determined by X-ray diffraction. Crystal morphology was analyzed by polarized light microscopy. Interfacial rheology was performed with a shear rheometer equipped with a biconical disk geometry. The data presented by the authors shows a novel interfacial network formation mechanism which is intrinsic to the crystallization properties of the glycerides. Furthermore, the authors present evidence that the crystal morphology and polymorphism of the glyceride crystal plays a major role in the elasticity and strength of the interfacial layer. This work shows unprecedented methods to investigate glyceride crystals at the air/oil interface and the presented findings allow a mechanistic understanding on the formation of interfacial layers by glyceride crystals.