Functional and rheological properties of composite flour from sweet potato, maize, soybean and xanthan gum

Sweet potato flour (SP), maize starch (MS), and soybean flour (SF) blends were prepared in different proportions like: 60SP/20MS/19.5SF; 50SP/30MS/19.5SF; 40SP/40MS/19.5SF; 50SP/20MS/29.5SF; 40SP/20MS/29.5SF; and 30SP/40MS/29.5SF. The constant percentage of xanthan gum at 0.5% was added to each blend. Functional and rheological properties of the composite flour were examined and compared with wheat flour as control. Oil absorption index was not significantly different (P > 0.05) among the six blends of composite flour and wheat flour. As increasing of soybean flour levels, swelling power, and pasting viscosity of composite flours decreased, specific volume of bread also decreased as decreasing of soybean flour level in composite flours, but the firmness of bread increased. Physical and sensory analysis showed that composite flour with the proportion of sweet potato flour 40%, maize starch 40%, soybean flour 19.5% and xanthan gum 0.5% yielded acceptable breads.