Ultrasound-assisted phosphorylation of chicory polysaccharides: Structural modification, digestive behavior and fermentation properties.

Chicory polysaccharides (CI), rich in inulin-type fructans, are promising dietary fibers whose functionality is closely associated with structure. However, the effects of structural modification on their gastrointestinal behavior and subsequent microbial fermentation remain unclear. In this study, ultrasound-assisted phosphorylation was applied to CI, with matched controls used to distinguish treatment-associated changes from the effects of ultrasound alone. Ultrasound increased the phosphorus-based degree of substitution from 0.052 ± 0.006 to 0.089 ± 0.004, while CI, ultrasound-treated CI (UCI), and ultrasound-assisted phosphorylation product (CP) retained closely overlapping unimodal molecular-weight distributions; FT-IR and 31P NMR further supported product-associated phosphorus in CP. Compared with UCI, CP showed 21.1-49.5% lower apparent IC₅₀ values across radical-scavenging and α-amylase/α-glucosidase inhibition assays. During simulated gastrointestinal digestion, CP showed lower intestinal-phase total-carbohydrate recovery than CI, whereas comparable net increases in reducing sugars (0.50 vs. 0.54 g per 100 g) indicated altered carbohydrate recovery rather than enhanced hydrolysis. After 24 h of fecal fermentation with microbiota from four healthy donors, CP produced more total SCFAs than CI (32.37 ± 1.34 vs. 27.77 ± 0.99 mM) and was associated with a distinct microbial community, with FDR-supported increases in Lactobacillus, Bifidobacterium, and Prevotella. Overall, ultrasound-assisted phosphorylation altered the in vitro functional and fermentation characteristics of chicory fructans without appreciable disruption of their principal molecular-weight distribution.