Structuring of edible oils by mixtures of γ-oryzanol with β-sitosterol or related phytosterols

The relation between molecular structure of oil-structuring agents and their gel-forming capability was investigated for mixtures of the phytosterol ester γ-oryzanol with a series of phytosterols. Dihydrocholesterol, cholesterol, β-sitosterol, and stigmasterol were found to form firm transparent gels with γ-oryzanol in sunflower oil under the conditions used in this work. The mixture of β-sitosterol with γ-oryzanol in sunflower oil does not gel immediately on cooling, but mechanical agitation such as shear promotes gelling. Gels that are formed immediately after cooling show a higher modulus than gels for which there is a time delay between cooling and agitation (150 vs. 100 kPa). The effect of oscillatory shear parameters (amplitude, frequency) is small, as long as the yield stress of the gel is not exceeded. The gels withstand compression very well (up to deformations of 10%), but yield at very small deformations. The enthalpy of melting of the solid phase is estimated to be 26±4 kJ/mol, putting it in the same range as for certain fibrillar steroid-derived organogels.