Xiaolong Shen

Ultrasound treatment can alter the functional properties of flour systems by modifying the organization of starch, protein, lipids, and other matrix components. In this study, whole tiger nut flour (WTF) and defatted tiger nut flour (DTF) were treated with probe ultrasonication at nominal power settings of 0, 300, 600, and 900 W. Pasting behavior, gel rheology, thermal transitions, X-ray diffraction (XRD), protein electrophoretic profiles, intrinsic fluorescence, and emulsifying properties were evaluated to assess how endogenous lipids influence ultrasound-induced changes in tiger nut flour. The response to ultrasound depended on both flour type and the property measured. In WTF, peak viscosity increased at 300 W and decreased at higher power settings, whereas DTF showed a non-monotonic pasting response with partial recovery at 900 W. The storage modulus of WTF gels was highest at 600 W, whereas the rheological response of DTF was comparatively small and non-monotonic. Sonicated WTF exhibited a broad diffraction feature near 2θ ≈ 20°, which is consistent with, but does not confirm, the presence of V-type amylose-containing structures. Differential scanning calorimetry revealed high-temperature endothermic transitions whose origin could not be assigned unambiguously, because starch-related transitions, protein denaturation, water redistribution, and other matrix effects may overlap in whole-flour systems. SDS-PAGE showed no visible change in the molecular-weight distribution of the major extracted proteins. The emulsifying activity and stability of the extracted protein fractions increased up to 600 W and declined at 900 W. Collectively, the results show that endogenous lipids are associated with distinct ultrasound responses in tiger nut flour. However, the present evidence does not directly establish amylose–lipid complex formation, starch–protein complexation, or a specific lipid-mediated protein-protection mechanism; direct structural analyses are required to verify these possibilities.

Astaxanthin (AST), despite its high bioactivity, exhibits poor stability and low bioavailability due to its strong lipophilicity and inherent degradation susceptibility. To overcome such a challenge, we developed a food-grade oleogel delivery system using a soy protein–arabinoxylan (SA) glycosylated complex modulated by different concentrations (0.5–3%) of sucrose ester (SE) or soy lecithin. We show that the emulsifier concentration has a non-linear effect on the oleogel microstructure: an optimal level of 1% had a significant impact on the interfacial compactness and network density, giving rise to improved thermal stability, rheological strength and AST encapsulation efficiency (81.27%). During in vitro digestion, the SA matrix in combination with emulsifiers allowed gastric protection and intestinal-targeted release of AST with a bioaccessibility of up to 88.84% (SAO-SE-AST). This controlled release profile directly translated into enhanced in vivo antioxidant efficacy in wild-type Bristol N2 Caenorhabditis elegans, as evidenced by reduced lipofuscin accumulation, elevated thermotolerance (survival rate: 64.44–73.33%), suppressed reactive oxygen species levels and activation of endogenous antioxidant enzymes (superoxide dismutase as well as glutathione peroxidase). Collectively, this research has uncovered that food-grade emulsifiers are not only stabilizers, but also key regulators of oleogel architecture and bioactive functionality. These results provide a structure–digestion–bioactivity correlation for protein–polysaccharide oleogels, representing a rational design strategy for high-performance delivery systems of lipid-soluble nutraceuticals.