Hydrothermal-assisted co-recovery of pectin, phenolics, and sugars from apple pomace coupled with understanding dietary fibre development via compositional, structural, and physicochemical modulations

This study presents a green hydrothermal process for co-recovering pectin, phenolics, and sugars from apple pomace (AP), followed by development of functional dietary fibres from the residual fibre-rich biomass. Optimized treatment at 120 °C for 15 min maximized recovery while minimizing pectin degradation and preserving phenolic antioxidant activity. The extracted pectin exhibited a degree of esterification of 84.5%, uronic acid content of 83.8%, and molecular weight of 161 kDa, with FTIR, 1 H NMR, TGA, rheology, and gelling properties confirming structural and functional similarity to commercial and acid-extracted pectin. The co-extracted phenolics-sugars extract was glucose-rich (92% w/w) with antioxidant activity and monosaccharides comparable to conventional ethanol extracts. Subsequent chemical (alkali, sodium hypochlorite) and mechanical (wet ball milling) modifications of HT produced fibres with diverse compositions, microstructures, and physicochemical properties, including zeta potential, particle size, and water contact angle. Chemical treatments generated cellulose-, cellulose + hemicellulose-, and cellulose + lignin-rich fibres with looser microstructures, enhanced hydrophilicity, and higher surface charges versus compact lignocellulosic fibres from ball milling. Cellulose-rich, highly charged, hydrophilic fibres with thin sheet-like structures exhibited high water-holding (26.44 g/g), swelling (24.48 mL/g), and glucose adsorption capacities (11 mmol/g), while lignin and oil containing porous cellulose-rich fibres demonstrated superior oil-holding capacity (19.7 g/g). Notably, HT fibres, enriched with pectin, protein, and oil, displayed amphiphilic surfaces, small particle size, and rough morphology, which contributed to their strong emulsifying capacity (EAI: 66.8 m 2 /g; ESI: 106.7 min). These findings highlight potential of green hydrothermal treatment for producing AP pectin, phenolics, sugars and reveal critical factors for developing functional dietary fibres from residual biomass. • Hydrothermal co-recovery of pectin, phenolics, and soluble sugar from apple pomace • Yields and properties of hydrothermal products matched those of conventional method • Cellulose and loose and charged structure governs hydration and GAC of apple fibres • OHC was driven by lignin and oil content with cellulose and loose fibre structure • Amphiphilic lignocellulose with pectin and protein boosts fibre emulsifying ability