Self-assemblies of lecithin and α-tocopherol as gelators of lipid material

Abstract

Amongst the different mechanisms that have been proposed and used to structure organogels, self-assembly of the gelators into supramolecular structures linked through non-covalent bonds is the most interesting. The gelator activity of LMGOs is often found most effective when micellar or lamellar phases are obtained, which is dependent on the gelator geometry and the specific packing parameter. Gelation can therefore be induced by altering the packing parameter of different gelators, but due to the law restrictions there are only a few edible gelators that can be used to structure edible lipids. Here, we show that a combination of α-tocopherol and phosphatidylcholine (PC) can be used to alter the packing geometry to provide supramolecular structures needed for the organogelation. We have observed that when the gelators were combined at 1 : 1 ratio in sunflower oil, edible organogels were obtained. The firmness of the solid-like material was enhanced when 1.0 wt% of water was added. The proposed mechanism for this assembly is that most likely cylindrical micellar structures are formed, due to combined assembly of the α-tocopherol and phosphatidylcholine, stabilized through physical interactions. Since these interactions, and the accompanied packing geometry, depends on temperature and application of external stresses, the formation of the organogels showed reversibility when the organogels were subjected to shear or when the temperature was increased to values above 35 °C. Polarized microscopy along with small angle X-ray scattering were used to provide a hypothesis for the mechanism behind the gelation.