Rice bran wax-structured macadamia oleogels and temperature-responsive water-in-oil emulsions: Fabrication, characterization and astaxanthin delivery

Oil structuring has been considered as a promising design for fat replacement due to its high content of unsaturated fatty acids and solid fat-like texture. In this study, rice bran wax (RBW) was used as an oleogelator to construct astaxanthin-loaded macadamia oleogel system, and the crystal morphology, intermolecular force and rheological behavior of the oleogels were evaluated. The results showed that RBW formed a stable oleogel at low concentration (5.0 wt%), which was attributed to the formation of a network of RBW crystals held together by van der Waals interactions. Moreover, the oleogels exhibited excellent thixotropy and thermal reversibility. Meanwhile, stable oleogels enabled the preparation of surfactant-free W/O emulsions with excellent stability (≥ 21 days). Microstructure and X-ray diffraction results confirmed that the stability of the emulsions was attributed to the crystallization of the RBW. And the emulsions showed temperature responsiveness. Additionally, the presence of RBW reduced the release of fatty acids (49% to 25%) and the bioaccessibility of astaxanthin (20.3% to 10.9%) in the emulsion during simulated in vitro digestion. The results can provide guidance for the development of novel solid fats, emulsions without surfactants, and functional foods with regulated lipid digestion and controlled nutrient release profiles. • RBW-based oleogels exhibited excellent thixotropy and thermal reversibility. • W/O emulsion without surfactant was prepared with RBW-based oleogel as continuous phase. • The presence of RBW reduced the bioaccessibility of astaxanthin in the emulsion. • RBW-based oleogel and W/O emulsion have the potential to mimic fat functionality.