The effect of chemical treatment on the In vitro hypoglycemic properties of rice bran insoluble dietary fiber

The in vitro hypoglycemic properties of three different sulfuric acid (H2SO4) modified rice bran insoluble fibers (SMRBIFs) produced using 0.2% (0.2%-SMRBIF), 1.25% (1.25%-SMRBIF), 2.0% (2.0%-SMRBIF) (W/v) H2SO4 in combination with 1.25% potassium hydroxide (KOH) respectively, were investigated. The results revealed that all the three RBIFs have strong glucose adsorption capacity and alpha-amylase inhibition activity, with 1.25%-SMRBIF being the most effective one. The glucose adsorption capacity increased with increasing porosity and specific surface area of the SMRBIFs, and the maximum glucose bound amount increased by 2-3 folds for acid-alkaline treated RBIFs compared to untreated material. The a-amylase inhibition activity of RBIF was associated with the formation of amylase-RBIF complex as confirmed by fluorescence spectroscopy, with the highest amylase activity inhibitory (24.72%) for 1.25%-SMRBIF. However, the glucose diffusion was retarded a bit stronger by these RBIFs compared to the untreated rice bran, which might be attributed to their larger specific surface area. Therefore, it was suggested that the concentration of postprandial serum glucose lowered by RBIF was mainly ascribed to binding glucose and retarding alpha-amylase action. (C) 2015 Elsevier Ltd. All rights reserved.