Abstract
The phase behavior of binary mixtures of γ-oryzanol and β-sitosterol and ternary mixtures of γ-oryzanol and β-sitosterol in sunflower oil was studied. Binary mixtures of γ-oryzanol and β-sitosterol show double-eutectic behavior. Complex phase behavior with two intermediate mixed solid phases was derived from differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) data, in which a compound that consists of γ-oryzanol and β-sitosterol molecules at a specific ratio can be formed. SAXS shows that the organization of γ-oryzanol and β-sitosterol in the mixed phases is different from the structure of tubules in ternary systems. Ternary mixtures including sunflower oil do not show a sudden structural transition from the compound to a tubule, but a gradual transition occurs as γ-oryzanol and β-sitosterol are diluted in edible oil. The same behavior is observed when melting binary mixtures of γ-oryzanol and β-sitosterol at higher temperatures. This indicates the feasibility of having an organogelling agent in dynamic exchange between solid and liquid phase, which is an essential feature of triglyceride networks.
Highlights
Mixtures of plant sterols (e.g., γ-oryzanol and β-sitosterol) can be potentially used as an alternative to crystalline fats like triacylglycerols (TAGs) for structuring the oil phase of some food products
The present paper investigated the phase behavior of binary and ternary mixtures of γ-oryzanol + β-sitosterol with and without sunflower oil
It complements the earlier study by AlHasawi and Rogers [14], which investigated a larger area of the phase diagram, in the sense that the present study takes a deeper look into a few specific changes in these systems and does not consider the full phase diagram of the ternary system
Summary
Mixtures of plant sterols (e.g., γ-oryzanol and β-sitosterol) can be potentially used as an alternative to crystalline fats like triacylglycerols (TAGs) for structuring the oil phase of some food products. Some studies reported on the use of plant sterol (ester + sterol) mixtures (γ-oryzanol and β-sitosterol) for the preparation of organogels and emulsions [6,7,8,9,10,11,12]. The formation of tubules is driven by enthalpy changes, indicating that the molecular interaction between γ-oryzanol and β-sitosterol determines the properties of the resulting gel to a large extent [12, 13]. The physical and mechanical properties of the gel, including firmness, transparency, melting and tubular microstructure, were found to be dependent on the γ-oryzanol to
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