Insoluble fiber-rich fractions derived from Averrhoa carambola: hypoglycemic effects determined by in vitro methods

The hypoglycemic effects of several insoluble fiber-rich fractions (FRFs) including insoluble dietary fiber, alcohol-insoluble solid, and water-insoluble solid isolated from the pomace of Averrhoa carambola were investigated by some in vitro methods. This study evidenced that these three insoluble FRFs could effectively adsorb glucose, retard glucose diffusion, postpone the release of glucose from starch, and inhibit the activity of alpha-amylase to different extents. All of these mechanisms might create a concerted function in lowering the rate of glucose absorption and as a result decrease the postprandial serum glucose concentration. Our results revealed that the hypoglycemic effects of these insoluble FRFs were significantly (P < 0.05) stronger than that of cellulose. Therefore, it was suggested that they could be incorporated as low-calorie bulk ingredients in high-fiber foods to reduce calorie level and help control blood glucose concentration. (C) 2003 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.