Physicochemical and in vitro functional properties of crude insoluble fiber-rich fractions from date fruit ( Phoenix dactylifera L.) pomace

Date fruit pomace (DFP), generated during date syrup production, remains underused despite its potential as a source of fiber-rich ingredients. This study evaluated the water-washed crude insoluble fiber-rich fractions (CIFs) from Barhi (soft), Shishi (semi-dry), Neghal (dry) and industrial mixed pomace (INP). The CIFs were compared in terms of yield, proximate composition, structural features, thermal behavior, water- and oil-holding capacities, particle-width increment (PWI), radical-scavenging activity of methanolic extracts and in vitro glucose and cholesterol adsorption. CIF yield ranged from 4.12 to 24.01%, with INP showing the highest yield and Barhi the lowest. Neghal had the largest particle size and the highest oil-holding capacity, while INP showed the highest PWI. Methanolic extracts from Neghal and INP showed stronger radical-scavenging activity in the DPPH and ABTS assays than those from Barhi and Shishi. FTIR and XRD showed general lignocellulosic features, while SEM revealed a more disrupted surface in INP and EDS detected Si signals in Neghal and INP. In vitro screening showed that glucose and cholesterol adsorption varied among CIFs and test concentrations, with Neghal showing the highest values under selected conditions. These results show that pomace source affected the properties of the crude fractions. Further studies should be conducted to determine the dietary fiber composition of these fractions using standardized AOAC methods and evaluate their incorporation into food systems.