The role of edible oils in low molecular weight organogels rheology and structure

Abstract

In this paper, the role of solvent characteristics on the rheological and physicochemical properties of organogels was investigated using different techniques. Vegetable oils, such as rice, sunflower and castor oil were used as solvents, for producing organogels with monoglycerides of fatty acids or a mixture of fatty alcohols (policosanol) as gelators. Moreover, two non-edible oils (silicon and paraffin oil) were also used for analysing the properties of solvents completely different in nature with respect to the edible ones, for a better interpretation of the given results. Organogels were investigated from a rheological point of view and through a microscopic analysis, given by polarised light (POM) and atomic force (AFM) microscopy, and X-rays to study the crystallinity of the system. The IR technique was used to analyse the intermolecular interactions, resulting in interesting information about the effect of oil polarity on the driving forces promoting structuration. This investigation showed that when solvents of a similar chemical nature are used, their physical properties, mainly oil polarity, are strictly related to the properties of the organogel, such as the onset of crystallisation temperature, the stiffness of the final material and its crystallinity. Anyway, these physical parameters seem insufficient to describe properly the role of solvents when oils of a different chemical nature are compared.

Keywords: Atomic force microscopy (AFM); Fourier transform infrared spectroscopy (FTIR); Interfacial tension (IFT); Organogels; Polarised optical microscopy (POM); Polarity; Rheology; X-ray.