Effects of extrusion on dietary fiber and isoflavone contents of wheat extrudates enriched with wet okara

Okara is the residue left after soymilk or tofu production. In North Americ a, okara is used either as animal feed, fertilizer, or landfill. The purpos e of this study was to use wet okara to produce and enrich extruded cereal products and to study the effects of extrusion on the dietary fiber and iso flavone contents. Wet okara was combined with soft wheat flour to produce t wo different formulations (33.3 and 40% okara) and extruded using four comb inations of two screw configurations and two temperature profiles. Various physicochemical properties, dietary fiber by enzymatic-gravimetric method, and isoflavone content by HPLC were analyzed. The radial expansion ratio de creased as fiber content increased. On the other hand, both bulk density an d breaking strength increased as fiber content increased. Combining okara w ith soft wheat flour resulted in increased protein, dietary fiber, and isof lavone contents compared with soft wheat flour alone. Extrusion of the form ulations resulted in decreased insoluble fiber (less than or equal to 25.5% ) and increased soluble fiber (less than or equal to 150%) contents of extr udates. Extrusion decreased the total detectable isoflavones (less than or equal to 20%) and altered the distribution of the six detected isoflavones.