Liquid oil-based structurant strategies have been the focus of extensive research in recent years due to a wide range of potential applications in several industries. Phytosterols and oryzanol can self-assemble into a fibrillar network that entraps liquid oil in the form of a gel. The goal for this research was to analyze the physical and mechanical properties of phytosterol oleogels (POs), composed of g-oryzanol (GO) and β-sitosterol (BS), with sterol concentrations of 15% and 20% wt., prepared using three different cooling rates (2, 5, and 20°C/min).<br/><br/>POs were prepared with GO to BS ratios of 1:4, 1:9, 1.5:1, and 4:1 w/w. Analysis of the microstructure of the POs were conducted using differential interference contrast (DIC) microscopy. Rheological properties were measured using an oscillatory sweep test. Oil binding capacity and opacity of POs were also determined. It was found that both the GO to BS ratio and the cooling rate significantly affected the structure and behavior of the POs. POs prepared with GO to BS at the equimolar concentration (approximately 1.5:1 w/w) showed high oil binding capacity, transparency, and mechanical properties. In contrast, it was observed that in excess of either of the sterol components these properties significantly decreased. For instance, when comparing the 15% wt. PO, 1.5:1 GO:BS ratio to the 1:9 GO:BS, a decrease of 28% and 41% were observed for oil capacity and transparency respectively. DIC images revealed the presence of crystalline structures corresponding to individual BS or GO in samples with a surplus of either of these components; which translates into an increase of the systems’ opacity. In the equimolar POs, slow cooling rates led to gels with higher mechanical properties, oil binding capacity, and superior transparency. The results suggest that the ability of the gel fibrillar network to further develop under the specific conditions. On the contrary, fast cooling rates impede the proper network self-assembly which typically resulted in lower opacities, further the matrix’s inability to bind oil, and diminish rheological properties. In the other GO:BS ratios, a different trend was evident. In POs high in GO or BS, fast cooling rates generated small crystalline structures which contribute to higher mechanical properties, greater transparency, and ability to bind oil. The results from this study showed that cooling rate and GO:BS ratio can be utilized interchangeably to tailor desired characteristics in POs.

Effects of cooling rate on g-oryzanol and β-sitosterol oleogels

253rd National Meeting (2017)

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