Thermal processing improved dietary fiber quality of whole grain highland barley: Studies on structural, physiochemical and functional properties

The effects of thermal treatments including atmospheric boiling (AB), high-pressure boiling (HPB), and baking (B) on structural, physicochemical, and functional properties of dietary fiber (DF) of whole grain highland barley (HB) were investigated. Thermal treatments led to the breakage of 3, 4-linked rhamnopyranose and 2-linked mannopyranose and decreased molecular weight and decreased fractions of rhamnose and mannose of water-soluble dietary fiber (SDF). The glucose molar ratio of SDF of AB-HB, HPB-HB and B-HB was increased by 53.18%, 51.52% and 47.75%, respectively, compared to that of control HB. Thermal treatments resulted in lower apparent viscosity, storage modulus (G′), and loss modulus (G″) of water-insoluble dietary fiber (IDF). Thermal treatments decreased the particle size and increased the specific surface area of DF, which increased the adsorption capacity of DF including glucose adsorption capacity, cholesterol adsorption capacity and nitrite adsorption capacity compared to those of control HB. In addition, thermal treatments increased the antioxidant activities, and inhibitory capacities against pancreatic lipase of DF. HPB and B treatments increased the inhibitory effect of SDF against α-amylase and α-glucosidase, and inhibitory effect of IDF against α-glucosidase. This study provided insights into DF of thermally-treated HB in the applications of functional foods.