Effect of three modification methods on physical and functional properties of flaxseed cake dietary fiber

Flaxseed cake dietary fiber (FCDF) is an important by-product of the oil manufacturing industry, but the low bioactivity limits its application. To improve the physical and functional properties of FCDF, it was separately treated using acidic (AC), cellulase (CE), and acrylate-grafting (AG) methods. Compared with the untreated FCDF, FCDF modified by AC (FCDF-AC), CE (FCDF-CE), and AG (FCDF-AG) had looser surface structures and greater flow characteristics. The hydration capacities were higher for FCDF-AC and FCDF-AG than for FCDF-CE. After modifications, FCDF showed high adsorption capacities to lipids, cholesterol, and nitrite ions. Moreover, the hypoglycemic properties of FCDF-CE and FCDF-AG, including glucose absorption capacity (GAC), glucose dialysis retardation index (GDRI), and α-amylase inhibition activity (AIA), were higher than those of untreated FCDF. In contrast, the GAC, GDRI, and AIA were not significantly different between FCDF-AC and FCDF (p > 0.05). Therefore, these results suggest that modified FCDF can be used as an additive in hypolipidemic and hypoglycemic foods. •Hydroxyl groups in the microstructure of FCDF were exposed after modifications.•FCDF-AC and FCDF-AG showed the high capacity of hydration and cation exchange.•The hypolipidemic properties were improved in FCDF-AC, FCDF-CE, and FCDF-AG.•FCDF-CE and FCDF-AG exhibited potential hypoglycemic capacities.