Valorization of orange peel by-products via ultrasound-pretreated enzymatic extraction of soluble dietary fiber: Structural and functional characterization.

Agro-industrial by-products valorization has attracted increasing attention due to their potential as sustainable sources of bioactive compounds, particularly dietary fibers. In this study, orange peel by-products were used as a raw material for the recovery of soluble dietary fiber via enzymatic extraction and ultrasound-pretreated enzymatic extraction. Ultrasound-pretreated enzymatic extraction achieved a soluble dietary fiber recovery of 26.04 ± 0.81% with approximately 90% purity. The content of phenolic compounds bound to soluble dietary fiber ranged from 3.23 ± 0.03 to 12.15 ± 0.21 mg GAE g-1. Soluble dietary fiber obtained by alkaline extraction exhibited higher water-holding capacity (9.16 ± 0.08 g g -1). Enzymatic extraction caused structural modifications and partial depolymerization, reducing fiber porosity and water affinity. Oil-holding capacity ranged from 1.08 ± 0.12 to 1.24 ± 0.05 g g-1, with no differences among extraction methods. Ultrasound-pretreated enzymatic extraction produced soluble dietary fiber with a more amorphous structure, lower crystallinity, greater surface disruption, and higher thermal stability. Moreover, it is a suitable substrate for the growth of mammalian intestinal symbionts such as Faecalibaculum rodentium and Bacteroides thetaiotaomicron, species recognized as beneficial for host health. Ultrasound pretreatment is a promising strategy for recovering high-value soluble dietary fibers from orange peel by-products, thereby enabling the production of tailored functional ingredients for food applications.