Optimization of extrusion process parameters for preparing fiber-rich oat flour

In this study, the effect of extrusion temperature and screw speed on the nutritional properties of the extrudates was evaluated by using a response surface methodology. The total, soluble, insoluble dietary fiber, beta-glucan, resistant starch, and total starch contents were evaluated through enzymatic assays. The processing parameters affected the content of all constituents of the flour mixture, except for beta-glucan. The total starch content, insoluble dietary fiber, and resistant starch were significantly decreased with increasing temperature and screw speed (until 13, 12, and 97%, respectively). The extrusion parameters had a positive effect on total dietary fiber content (increased this parameter up to 29%) when compared with the raw material, that is, oat and rice blend, causing changes from the insoluble to soluble dietary fibers. In the electron microscopic analysis, the structure of all extrudates showed to be homogeneous and compact with irregular surfaces.