Structuring in β-sitosterol + γ-oryzanol-based emulsion gels during various stages of a temperature cycle

Water-in-oil emulsions were prepared, structured only by a mixture of sitosterol and oryzanol and without further emulsifiers, containing 16 and 32% total sterol(esters)s on lipid phase and 10, 30 or 60% water. Previously, mixtures of β-sitosterol + γ-oryzanol were shown to form self-assembled tubules in triglyceride oil with diameter 7.2 ± 0.1 nm and a wall thickness 0.8 ± 0.2 nm. At 16% total sterol concentration, the SAXS diffraction patterns only demonstrate the presence of sitosterol and oryzanol crystals, but not of tubules. At 32% total sterol concentration, the diffraction patterns reveal the presence of tubules next to the crystals of the individual compounds. However, the tubule structure in these emulsions was more complicated than in pure oil and changed during storage, revealing the formation of bigger structures in the emulsion over time. In the cooling stage of a temperature cycle, water droplets nucleate at the tip of the fibres that reappear as a consequence of crystallisation.

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