Optimisation of the Chemical Composition of Sorghum-based Flour Blended with Plantain and Tigernut Flours to Produce Nutritional and Physicochemically Quality Composite Flour

Composite flour of sorghum flour with plantain and tigernut flours were produced in order to enhance its nutritional contents. Experimental design was carried by using optimal model mixture design of response surface methodology with sorghum flour (70–90%), plantain flour (5.36–20%) and tigernut flour (2.99–10%) as the independent variables, while the dependent variables were the proximate composition and functional properties. The optimum blends with overall best fibre and protein contents obtained were runs 2 (90% sorghum, 0% plantain and 10% tigernut flours) which had 1.29% fibre and 10.15% protein contents; run 6 (75.92% sorghum, 14.08% plantain and 10% tigernut flours) with 1.19% fibre and 8.05% protein contents, run 7 (70% sorghum, 20% plantain and 10% tigernut) with 1.29% fibre and 8.53% protein contents; and run 11 (82.43% sorghum, 7.57% plantain and 10% tigernut flours) with 0.79% fibre and 9.80% protein contents. Substitution of sorghum flour with plantain and tigernut flours however reduced the water absorption capacity of the optimised composite flours. In addition, substitution of sorghum flour with plantain and tigernut flour at 20% and 10% significantly (p = 0.05) increased the resistant starch and soluble dietary fibre which helps in reduction of the glycemic index of the composite flour. The study therefore showed that addition of plantain and tigernut flour (20% and 10%) to sorghum flour to produce composite flour greatly enhanced its nutrient quality, and specifically, the protein, fibre and mineral contents, as well as the resistant starch, soluble fibre, pasting characteristics, antioxidant properties with attendant low glycemic index.