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 (WHSDF), quinoa soluble dietary fiber (QUSDF) displayed a compact structure, higher reducing power and digestive enzyme inhibitory activity. WHSDF showed stronger DPPH radical scavenging activity than QUSDF. Quinoa insoluble dietary fiber (QUIDF) and wheat insoluble dietary fiber (WHIDF) displayed similar network structure, but the α-glucosidase inhibitory activity of WHIDF was higher than QUIDF. Moreover, the bound polyphenols in QUIDF and WHIDF 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.