Enhancement of physical and chemical properties of rice hull via Huangshui bioconversion for improved Baijiu quality

• Huangshui pretreatment reduced rice hull test weight to 87.04 g/L ( p < 0.05). • Treated rice hulls significantly decreased furfural (49.02 %, p < 0.01) in Baijiu. • Hexanoic acid and key esters increased by 25.22 %−69.95 % with Huangshui pretreatment. This study investigated Huangshui fluid pretreatment effects on rice hull's physical properties and furfural removal, revealing optimal conditions (solid-liquid ratio 1:15, pH 3.2, 60 °C, 6 days) achieving furfural reduction to 68.55 ± 0.33 mg/100 g (below harmful thresholds), while reducing test weight to 87.04 ± 0.749 g/L ( p < 0.05) without compromising water absorption/elasticity ( p > 0.05). Gas chromatography demonstrated Huangshui-treated rice hulls enhanced crude Baijiu quality: acetaldehyde decreased 38.30 % ( p < 0.01), furfural 49.02 % ( p < 0.01), methanol 9.37 %, fusel oil 6.31 %, while hexanoic acid increased 25.22 %, ethyl hexanoate 69.95 %, and four major esters 24.45 %. The pretreatment significantly improved mash looseness and flavor profiles, confirming its feasibility for reducing harmful compounds and upgrading Baijiu quality through effective impurity removal and ester enrichment.