Processing-induced matrix remodeling of insoluble dietary fiber from soybean hulls and its impact on physicochemical properties and in vitro fermentation behavior.

This study compared the physicochemical properties and in vitro fermentation behavior of four insoluble dietary fiber-rich residual fractions from soybean hulls (IDF-SH) generated by different polysaccharide extraction protocols. Although the extraction strategy did not alter the major functional groups or crystal structure of IDF-SH, it markedly changed its microstructure. In particular, microwave treatment transformed the compact matrix into a looser architecture, and the extent of this reconstruction depended on the extractant system. These structural differences were closely associated with pronounced changes in hydration, adsorption, and fermentation properties. Among the four samples, the IDF-SH obtained by microwave-assisted ammonium oxalate extraction produced the highest level of SCFAs during in vitro colonic fermentation. Microbiota and correlation analyses further indicated that its superior fermentability was associated with the enrichment of fiber-degrading and SCFA-associated taxa, particularly Lachnospira and Bacteroides. These findings indicate that IDF-SH is an insoluble matrix remodeled during polysaccharide extraction, and that its functional properties are strongly influenced by the extraction process.