Blends of sorghum and Bambara groundnut flour at 90:10, 80:20 and 70:30 ratios respectively, were extruded at 20%, 22.5% and 25% moisture levels and 120 o C, 140 o C and 160 o C barrel temperatures using a single-screw extruder. Response surface methodology with central composite face-centered (CCF) design was used to model the viscosity, water absorption index (WAI) water solubility index (WSI), sectional expansion index (SEI), bulk density (BD), apparent specific volume (ASV) and mass flow rate of the extrudates. , and 1.19 to 2.3 g/s respectively. The R 2 values were 0.83, 0.71, 0.55, 0.61, 0.66, 0.77 and 0.61 respectively with a non-significant lack of fit; except for viscosity. Plots of residuals against fitted values showed that residuals were randomly scattered in all cases, thus validating the empirical models for the responses. The optimum amount of Bambara groundnut flour, feed moisture and extrusion temperature were established for viscosity, WAI, SEI, BD, ASV and MFR of the extrudates. Feed moisture had the most effect on extrudates functional and physical properties followed by extrusion temperature.

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Legumes and cereals stand a great chance as remedies to overcome incidences of protein malnutrition and oxidative stress. Cereal grains such as wheat (WT), millet (ML), maize (MZ) and acha (AC) were blended with cowpea (CP), peanut (PN) and soybean (SO) at varying levels to produce four different blends. Protein contents of the cereal-legume blends were determined and found to be higher as the inclusion level of legumes increased in the blends. Amino acid profiles and antioxidant properties of the flour blends were evaluated. Results showed that leucine was the most abundant (6.52-8.45 g/100 g) essential amino acid in the flour blends while total content of essential amino acids increased as the level of legume incorporation increased in the WT/SO (31.3-36.2 g/100 g) and MZ/CP (34.5-37.4 g/100 g). The antioxidant properties showed that MZ50:CP50 exhibited greater ferric reducing antioxidant power while WT70:SO30 and AC50:SO50 had stronger metal chelation activity and ML50:PN50 scavenged the most DPPH radicals when compared to the other flour blends. The results suggest that the composite flours have the potential to be used as ingredients for the formulation of food products with high levels of essential nutrients in addition to antioxidant benefits.

Multi-parameter extrusion cooking conditions for the extrusion of composite flours of rice and soybean were modeled using response surface methodology (RSM). A five-level-three-factors central composite rotatable design (CCRD) was employed to optimize three process variables including barrel temperature (BRT)(X 1 ), feed moisture (FMC)(X 2 ) and feed soybean composition (FSC)(X 3 ) for the achievement of satisfactory hydration characteristics and proximate composition. The fitted polynomial models indicated significant coefficients, satisfactory coefficients of determination (R 2 and R 2 adjusted ) and non-significant lack-of-fit test. Optimum X 1 , X 2 and X 3 were 120˚C, 20%, and 23% for rice-soybean based extrudates. At these optimum combinations, optimum responses were 97.10% for dispersibility, 6.11 water absorption index and 8.42 water solubility index, while proximate composition of 1.02% moisture content, 3.62% lipid, 26.26% protein, 0.48% ash content, 2.14% fibre, 70.13% and 412.14 kcal/100g of energy were obtained. Under the optimized conditions, the responses are well matched with the predicted values and therefore the models could be used to predict the extrusion system in its natural state.

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