Rheological properties of beta-sitosterol and gamma-oryzanol organogels

The aim of this work was to study the rheological properties of sunflower oil organogels (OGs), produced with beta-sitosterol and gamma-oryzanol, in comparison with the rheological properties of butter, in order to identify the most suitable structures to be used in a baked product. OGs were prepared by dispersing different sterol amounts in warm sunflower oil (75°C) reaching final concentrations of 3.1, 3.5, 4.0, 4.5, 5.0, 5.5, 5.9%, while maintaining a 2:3 ratio (w/w) between the two sterols. Gel formation occurred at all the gelator concentrations and the samples had different rheological properties. All gels showed a solid-like structure with storage modulus (G’) higher than loss modulus (G’’) and a shear thinning behaviour as complex viscosity decreased when frequency increased. G’ and G” were affected by the gelator concentration, with a sharp increase of both moduli from 4.0 to 4.5%. Moreover, OG prepared with 4.5% gelator concentration showed mechanical spectra similar to those of butter.