Polysaccharides from Chinese Baijiu by-products: Structural remodeling, cascade valorization, and functional food applications: A review.

Chinese Baijiu production generates massive solid (Jiuzao) and liquid (Huangshui) by-products annually, which are rich in structurally distinct polysaccharides shaped by long-term solid-state fermentation (SSF). This review critically synthesizes current knowledge on the extraction, structural characterization, and bioactivities of these polysaccharides, with emphasis on SSF-driven structural remodeling. Jiuzao polysaccharides are dominated by feruloylated arabinoxylans with a β-1,4-linked xylan backbone and arabinose-to-xylose ratios of 0.3-0.9, while Huangshui polysaccharides are enriched in soluble glucans (3-80 kDa) adopting triple-helix conformations and containing up to 31.8% sulfate. These structural features, particularly feruloylation, molecular weight (Mw) distribution, and higher-order conformation, are associated with antioxidant, immunomodulatory, prebiotic, and hepatoprotective activities through emerging structure-activity relationships. Feruloylated arabinoxylans exhibit a dual prebiotic-antioxidant function, whereas Huangshui glucans have been reported to exhibit immunomodulatory activity, with conformation- and receptor-related mechanisms proposed based partly on evidence from structurally analogous polysaccharides. We critically evaluate advanced extraction technologies (ultrasound, microwave, enzyme-assisted, twin-screw extrusion) and discuss the purity-function trade-off, proposing that moderate purity retaining synergistic phenolics is often more functionally favorable than exhaustive purification for food applications. A cascade valorization model integrating polysaccharide extraction with full-component utilization is outlined, potentially improving overall resource efficiency through integrated utilization of multiple components. This review establishes a comprehensive structural-functional framework for transforming Baijiu by-products into sustainable functional ingredients and biomaterials.