Optimised ultrasound treatments enhance hydration properties and induce structural modifications in dietary fibre concentrates derived from orange peels

Abstract

Recent studies have focused on the modification of individual soluble and insoluble dietary fibre (DF) fractions from fruit by-products to enhance the techno-functional properties of ingredients. However, the potential to improve these properties in DF concentrates while preserving the combined functionality of both fractions remains underexplored. This study aimed to optimise ultrasound treatment conditions—power (W), solid-liquid ratio (g/mL), and time (min)—to improve the hydration properties of DF concentrates derived from orange peels (OP-DFC) and to explore the structure–function relationships associated with ultrasound-induced modifications. Ultrasound treatments resulted in the selective enhancement of solubility (SOL, 320 W, 1:30 g/mL, 30 min), swelling capacity (SC, 80 W, 1:25 g/mL, 25.6 min), and water retention capacity (WRC, 208 W, 1:20 g/mL, 30 min), with increases of up to 60% compared with untreated OP-DFC. Simultaneous optimisation yielded the best compromise at 188 W, 1:28 g/mL, and 30 min. Enhancements in hydration properties were associated with cavitation-induced structural modifications, including matrix disruption, increased porosity, and partial depolymerisation of DF. These changes were reflected in a decrease in the insoluble DF content from 49.4% to 42.4–46.2% and an increase in the soluble DF content from 6.6% to 9.5–12.1%. From a technological perspective, increased SOL facilitates ingredient incorporation into foods while higher SC and WRC enhance rehydration behaviour and binder performance across a wide range of products. Overall, this strategy supports the development of clean-label, DF-rich ingredients from orange by-products with targeted hydration functionalities, broadening their potential use in diverse formulations.