Characterization of Extruded Sorghum-Soy Blends to Develop Pre-Cooked and Nutritionally Dense Fortified Blended Foods

Food aid commodities are essential food items in global food aid programming. Some are primarily made from an extrusion of corn and soybeans. However, there are concerns about the genetically modified organisms (GMOs) of some of these grains. Hence, there is a need for alternatives to grains, like sorghum, which is not GMO. It is critical to ensure that products from this new ingredient meet the quality requirements, hence the need to profile them. An expanded formulation sorghum-soy blend (SSB), obtained from extrusion cooking, was ground using a hammer mill and analyzed for changes in properties that were affected by the transformation of starch and protein during processing. Macro- and micro-nutrients were added to these milled blends to prepare fortified blended foods (FBFs) that could meet the recommendations of Food Aid Quality Review (FAQR) report on energy, protein, and micronutrient content. The water absorption index (WAI) ranged from 2.82 to 5.90 g/g, the water solubility index (WSI) ranged from 6.22 to 18.50%, and the blends were affected by the formulation-whole/decorticated sorghum and different levels of fat. Extrusion processing caused starch gelatinization in the range of 90.69-96.26%. The pasting properties indicated that whole grain blends of SSB had lower peak time and higher final viscosity when compared to decorticated sorghum blends. The Bostwick flow rate of cooked porridges with 20% solids was within the recommended range of 9-21 cm/min. Starch digestibility significantly increased after extrusion, with a 149.65% increase in rapidly digestible starch (RDS). The protein digestibility did not vary significantly when subjected to extrusion and wet cooking. There was a significant reduction in anti-nutritional factors in the extruded binary blends of SSB when compared to respective raw blends: phytic acid was reduced by 25.33%, tannins were not found, and trypsin inhibitors were reduced by 19.50%. Thus, the extrusion processing of SSB with the subsequent addition of macro- and micro-ingredients was effective in producing FBFs with high nutritive value, comparable to FBF made from traditional ingredients.