Comparative analysis of extraction methods on physicochemical and functional properties of soluble dietary fiber from...

Thinned young apples, often discarded during orchard management, represent an underutilized resource rich in soluble dietary fiber (SDF) and bioactive polyphenols. Valorizing these by-products into functional food ingredients aligns with sustainable agricultural practices and circular bioeconomy goals. In this study, we systematically compared the effects of three extraction methods (composite enzymatic, citric acid, and alkaline hydrogen peroxide) on the structural, physicochemical, and functional properties of SDF from thinned young apples. The extraction approach markedly influenced SDF yield, monosaccharide composition, molecular weight distribution, and associated bioactivities. SDF extracted by alkaline method exhibited the highest bound polyphenol contents and the lowest molecular weight, conferring superior antioxidant and nitrite adsorption capacities. In contrast, the higher molecular weight and viscosity of SDF extracted by citric acid method enhanced its glucose dialysis retardation and bile acid binding abilities, while SDF extracted by enzymatic method displayed the strongest oil-holding capacity due to its porous microstructure and hydrophobic surface characteristics. These results demonstrated clear structure-function correlations among the three SDFs. Collectively, this study provides new mechanistic insights into the extraction-dependent variations in SDF composition and bioactivity, and underscores the potential of thinned young apples as a sustainable source of multifunctional dietary fibers for food and nutraceutical applications.