Valorization of Panax ginseng residues: Functional fiber development through cross-linking combined with ultrasonication

Ginseng processing yields large amounts of dietary fiber (DF), but its dense structure, low hydration capacity, and limited functionality restrict direct use. Although several modification methods have been studied, the combined impact of cross-linking and ultrasonication on ginseng DF remains unclear. This study therefore aimed to enhance the physicochemical, structural, thermal, emulsifying, and functional properties of ginseng DF using chemical cross-linking alone (C) and cross-linking followed by ultrasonication (CU). Both treatments considerably improved the water-holding capacity, oil holding capacity and water swelling capacity of ginseng DF, with CU treatment resulting in the most significant improvements. Monosaccharide profiling revealed elevated glucose and galactose levels in CU-treated DF and increased galacturonic acid levels in C-treated DF. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses revealed that both treatments, particularly CU, increased crystallinity and altered molecular interactions in ginseng DF. Thermal analysis revealed enhanced thermal stability in CU-treated DF, as reflected by higher decomposition temperatures and residual mass. Rheological analysis showed increased apparent viscosity and shear-thinning behavior in modified fibers, which resulted in an improved network structure. CU treatment enhanced the antioxidant activity (DPPH, ABTS, and FRAP) of ginseng DF. Bile acid-binding capacity, cholesterol adsorption capacity, glucose adsorption capacity, and nitrite ion adsorption capacity were considerably higher in CU-treated DF than in ginseng residue and C-treated DF. In addition, CU-treated DF exhibited the highest ginsenoside content and superior emulsion stability, likely owing to reduced particle size and increased surface activity. These enhancements in functional and structural properties can be attributed to the molecular and conformational changes induced by the combined treatments, as evidenced by the results of scanning electron microscopy, XRD, FTIR, and thermogravimetric analyses. Overall, CU treatment can effectively improve the physicochemical and functional properties of ginseng DF.