Comparative study on the structure, physicochemical, and functional properties of dietary fiber extracts from quinoa and wheat

Soluble and insoluble dietary fiber (SDF and IDF) were extracted from quinoa and wheat. Results showed that all the dietary fiber (DF) samples exhibited typical infrared spectrum characteristics of polysaccharides. Compared with wheat soluble dietary fiber (WH SDF ), quinoa soluble dietary fiber (QU SDF ) displayed a compact structure, higher reducing power and digestive enzyme inhibitory activity. WH SDF showed stronger DPPH radical scavenging activity than QU SDF . Quinoa insoluble dietary fiber (QU IDF ) and wheat insoluble dietary fiber (WH IDF ) displayed similar network structure, but the α-glucosidase inhibitory activity of WH IDF was higher than QU IDF . Moreover, the bound polyphenols in QU IDF and WH IDF also showed better DPPH radical scavenging activity and α-amylase inhibitory activity. In summary, the DF of quinoa and wheat showed different structural, physicochemical and functional properties, and in both samples bound polyphenols had significant contributions to the antioxidant and hypoglycemic capacity of IDF. • The dietary fiber of quinoa and wheat showed different microstructure. • Quinoa soluble dietary fiber had higher hydroxyl radical scavenging ability. • Bound polyphenols contributed to the hypoglycemic capacity of quinoa dietary fiber.