Functional and sensory properties of soybean and sweet potato flour mixtures

Sweet potato flour was supplemented with full fat soy flour at a 10 to 90% level. Proximate composition, nitrogen solubility, water absorption capacity, bulk density, degree of starch gelatinzation, Amylograph pasting and organoleptic properties of the mixtures were evaluated. Nitrogen solubiliity indices of raw soybean flour and sweet potato flour ranged from 50 to 90% and 55 to 95%, respectively, with minimum values of 24 and 26% at pH 4. Heat action lowered solubility indices to a range of 12 to 20% and 14 to 23% for soybean and sweet potato floor, respectively. Increased addition of soybean flour to sweet potato flour slightly reduced the solubility of the mixtures at all levels of pH change. Water absorption capacity and bulk density decreased with increasing levels of soybean flour in the mixtures. Degree of starch gelatinization of fresh mixtures was about 50%. Amylograph results showed that sweet potato flour can tolerate tip to 20% full fat soy flour without losing its viscosity characteristics. Sensory evaluation of the sample mixtures showed that samples containing 20 to 40% full fat soy flour were scored higher in appearance, odour, texture and taste as compared with unsupplemented samples. © 1992.