The composition of edible oils modifies β‐sitosterol/γ‐oryzanol oleogels. Part II: Addition of selected minor oil components

The role of selected minor oil components on sterol/sterol ester oleogels was studied. Therefore, oleic acid, tocopheryl acetate and monoglycerides were admixed with three vegetable oils, having different fatty acid compositions. Before that, minor natural components were removed from untreated oils (purification). Moreover, purified oils were subjected to a humidity treatment to increase their water content. All additives retarded the molecular self‐assembly of sitosterol with oryzanol, and the effect was dose‐dependent. Gel hardness only increased at low concentrations of tocopheryl acetate and decreased in all gels at higher concentrations. In contrast, Gmax′ was invariable in samples with oleic acid and monoglycerides and increased in gels containing tocopheryl acetate and water. Therefore, Gmax′ does not necessarily relate to the gels' compression firmness. Atomic force microscopy showed that the microstructure of oleogels was considerably modified by the additives. In general, a packed surface of twisted, thick bundles of tubules may be associated with a stiffer gel. Moreover, a composite structure in gels with monoglycerides was visible and confirmed by differential scanning calorimetry (DSC). DSC was used to determine gel–sol transition temperature and was associated with the number of tubules in the gel. The gel–sol temperature increased in samples 1.0% w/w oleic acid and tocopheryl acetate and decreased in gels with monoglycerides and water. The results show that oleogel properties can be significantly modified by minor components with functional groups. That was associated with interactions with the sterol and sterol ester in solution and with the surface of the tubules (ferulic acid moieties of oryzanol) in oleogels.