In 1990, a well-known model to predict pure component properties of triglycerides was presented by Wesdorp in “Liquid-multiple solid phase equilibria in fats: theory and experiments” and has been shown to perform well despite making thermodynamically inconsistent predictions for certain test cases. In this study, the underlying parameter set is improved to deliver more physically consistent predictions, i.e., increasing melting point and enthalpy of fusion with increasing stability of the polymorphs, without deterioration of the primary model quality to describe the available experimental data. Interestingly, when a curated dataset containing only thermodynamically consistent data is compared to a broader dataset, it appears that the model’s efficacy is highly dependent on the quantity of data, specifically the number of unsaturated triglycerides data. Quality and thermodynamic consistency of model predictions and the condition of a reliable description of monoacid triglycerides as a subset is discussed, addressing a potential interdependence.
The first part of this study showed that the triglyceride composition of purified oils has little impact on sterol/sterol ester oleogels. Hence, changes in the gels’ properties observed in previous studies must arise from minor polar components, particularly by changing the interactions within the fibrillar network. Selected molecules (oleic acid, tocopheryl acetate, monoglycerides, and water) were added to three purified oils to unravel the individual contributions introduced by different functional groups. While all additives retarded the molecular self-assembly of sitosterol with oryzanol, distinct effects were found for gel hardness, transition temperatures and enthalpies, strain sweep responses, and microstructure. It was discovered that the maximum storage modulus in the linear viscoelastic region does not necessarily relate to the gels’ compression firmness. In samples comprising oleic acid and tocopheryl acetate, discrete interaction mechanisms with the scaffolding elements were suggested since results between the two additives developed differently and were dose-dependent. A network supporting effect was suggested at low concentrations, in line with previous results for oils comprising low levels of thermal deterioration products. The microstructure of oleogels was considerably modified with additives. Unfortunately, effects are difficult to quantify due to the packed surface observed in AFM micrographs.
The role of solvent composition, in particular, minor oil components on sterol/sterol ester oleogels, has been studied recently . Reportedly, deterioration products hamper network formation and modify the gel’s macroscopic properties, probably due to alterations of the scaffolding elements’ interactions. However, the role of the FA composition of TAGs has not yet been addressed. In this study, minor oil components of three vegetable oils with varying degrees of unsaturation (iodine values) were removed, and the oils were chemically and physically characterized before and after the treatment. Consequently, β sitostero/γ-oryzanol oleogels were produced, and the gel-sol (DSC) and sol-gel (rheology) transitions were monitored. Moreover, large and small deformation tests were performed, and the results were linked to oil parameters. In contrast to minor oil components, the FA composition has little impact on oleogel properties. The decline in gel hardness with IV is possibly linked to a lower solvent viscosity. However, a considerable drop in gel-sol transition temperature was observed with increasing IV indicating fewer elements of scaffolding. That was linked to the rapid formation of primary oxidation products in purified flaxseed oil during oleogel preparation, impairing tube formation. Similar to previous results on deterioration products, these minor components seem to aid network strength at low concentrations resulting in similar transition enthalpies and G’. That might be due to shifted network interactions in the presence of molecular species with functional groups. In the second part of this study, these modified interactions in the presence of selected minor components will be discussed.