Effect of Oil Type on Formation, Structure and Thermal Properties of γ-oryzanol and β-sitosterol-Based Organogels

Oil sources characterized of increasing viscosity and polarity (flax-seed oil, sunflower oil, extra virgin olive oil, triolein, castor oil) were gelled by using mixtures of β-sitosterol and γ-oryzanol (5, 10 and 20 % w/w). The gelling time, thermal properties as well as structure characteristics were determined. As the oil viscosity increased the gelling time increased. The effect of oil type resulted more evident as the structurant concentration decreased. Samples containing 5 % of the most viscous and polar castor oil did not gelled over the entire experiment. When gels were formed, the firmness of samples decreased in concomitance with modifications of thermal data as the oil viscosity increased. During storage at 20 °C the gels became stronger as consequence of the progression of the aggregation among sterol-sterol ester assemblages. Once again, less structurants were in the mixture more evident was the influence of oil type. These results were attributed to the increase of the difficulty of β-sitosterol and γ-oryzanol molecules to pack together as the oil viscosity increased.