Abstract: In order to improve the comprehensive utilization of dietary fiber from tartary buckwheat bran, the effect of steam explosion applied at different pressures for different durations was investigated on improving the physicochemical and functional of tartary buckwheat dietary fiber. The operating conditions were optimized based on soluble dietary fiber content. The monosaccharide composition, physicochemical properties and structural characteristics of the raw and treated dietary fiber were determined. The results showed that the contents of insoluble dietary fiber (IDF), cellulose, hemicellulose, lignin and pectin in tartary buckwheat bran were significantly decreased (P < 0.05), and the contents of soluble dietary fiber (SDF), soluble sugar, reducing sugar and total sugar were significantly increased after steam explosion treatment (P < 0.05). Furthermore, compared with the untreated sample, the content of SDF was increased by 54.11% (12.36 versus 8.02 g/100 g) under optimized conditions (1.2 MPa for 90 s). After the treatment, the monosaccharide composition of tartary buckwheat bran dietary fiber was changed, and the water-holding capacity, oil-holding capacity, swelling power, α-amylase-inhibitory activity, glucose absorption capacity and thermal stability were significantly enhanced. Moreover, more hydroxyl groups were exposed, and a loose multilayer honeycomb-like network structure was observed in the treated SDF. Steam explosion could be useful to increase the SDF content and improve the physicochemical properties of tartary buckwheat bran dietary fiber, which will provide theoretical references for the utilization of SDF from tartary buckwheat bran and the development of dietary supplements.

Key words: steam explosion; tartary buckwheat bran; modification of dietary fiber; physicochemical properties; structural characteristics