Rice bran wax structured oleogels and in vitro bioaccessibility of curcumin

Curcumin, the bioactive compound found in turmeric, exhibits a wide range of health-promoting properties. However, its application in food formulations and as nutritional supplements is limited by its poor bioaccessibility. This study investigates the effects of curcumin on the structure formation and physical properties of oleogels made with three different concentrations of rice bran wax (RBW) (2%, 6%, and 10% w/w) compared to an ungelled control oil and examines the bioaccessibility of curcumin contained in those lipid systems. The physical and structural properties were characterized using a penetration test, solid fat content, polarized light microscopy, differential scanning calorimetry, and X-ray diffraction (XRD). Data analysis revealed no significant differences in polymorphic or thermal properties between oleogels with and without curcumin; however, differences in microstructural properties were documented for oleogels with curcumin. Moreover, the percent of lipid crystallinity in 6% and 10% RBW oleogel increased in samples containing curcumin. An in vitro simulated digestion study showed that curcumin bioaccessibility significantly increased with increasing RBW content relative to the ungelled control. Results from this study provide insight into the potential utilization of RBW oleogels for delivering curcumin and other poorly water-soluble compounds in food, dietary supplement, pharmaceutical, and cosmetic products.