Effect of Dietary Fiber and Thermal Conditions on Rice Bran Wax-Based Structured Edible Oils

In this work, extra-virgin olive oil (EVO)- and sunflower oil (SFO)-based oleogels were structured using rice bran wax (RBW) at 10% by weight (w/w). Bamboo fiber milled with 40 (BF40), 90 (BF90) and 150 (BF150) mu m of average size was added as a structuring agent. The effect of fiber addition and cooling temperature (0, 4, and 25 degrees C) on thermal and structural parameters of achieved gels was assessed by rheological (both in rotational and oscillatory mode), texture, and differential scanning calorimetry tests. Oleogelation modified the rheological behavior of EVO and SFO, thus shifting from a Newtonian trend typical of oils to a pseudoplastic non-Newtonian behavior in gels. Moreover, oleogels behaved as solid-like systems with G ' > G '', regardless of the applied condition. All samples exhibit a thermal-reversible behavior, even though the presence of hysteresis suggests a partial reduction in structural properties under stress. Decreasing in cooling temperature negatively contributed to network formation, despite being partially recovered by low-granulometry fiber addition. The latter dramatically improved either textural, rheological, or stability parameters of gels, as compared with only edible oil-based systems. Finally, wax/gel compatibility affected the crystallization enthalpy and final product stability (gel strength) due to different gelator-gelator and gelator-solvent interactions.

Automated summary

In this study, oleogels were prepared using rice bran wax and bamboo fiber in olive oil and sunflower oil, and the effects of fiber addition and cooling temperature on the thermal and structural parameters of the gels were investigated. It was found that decreasing cooling temperature and adding low-granulometry fiber had a negative impact on network formation, but the negative effects could be partially recovered by the addition of low-granulometry fiber.