Okara dietary fiber and hypoglycemic effect of okara foods

Okara is the byproduct of tofu or soymilk production process. The okara used in this paper contains 58.60% total dietary fiber (TDF), 55.63% insoluble dietary fiber (IDF) and 1.91% soluble dietary fiber (SDF). Okara may be considered a good source of dietary fiber for the high fiber content, cheap cost and wide resource. Okara dietary fiber mainly consists of arabinose, galactose, xylose and galacturonic acid, and its molecular weight is from 724 kDa to 2081 kDa. Replacing 25%, 15% or 10% wheat flour with okara powder to make noodle, steamed bread or bread, the three okara foods have almost similar taste and quality to control foods. Their TDF contents increase from 7.97%, 13.83% and 14.97% to 25.71%, 21.95% and 22.73%, respectively, compared to control foods, and the enhancement is mainly IDF. The hypoglycemic effects of these okara foods were evaluated by glycemic index (GI) using in vivo study. The results showed the GI for okara bread, okara steamed bread and okara noodle were 49±8, 54±2 and 52±14, respectively, referring to glucose (GI=100). The GI of okara foods was distinctly lower than that of control foods (bread 67±3, steamed bread 86±10, and noodle 77±11). The hypoglycemic effect could be caused by okara dietary fiber. The study suggests that replacing part wheat flour with okara powder to make principal foods is a potential method for okara's application.