Effect of barrel temperature and feed moisture on protein quality in pre-cooked Kabuli chickpea, sorghum, and maize flours

Abstract

The effect of barrel temperature (120 and 150 ℃, held constant in zones 4–6) and feed moisture (20 and 24%) on the protein quality of Kabuli chickpea, sorghum, and maize flours were examined, which included amino acid profile, in vitro protein digestibility and in vitro protein digestibility-corrected amino acid score (IV-PDCAAS). It was found that the limiting amino acid of chickpea changed from threonine to valine after extrusion, whereas both sorghum and maize were limiting in lysine before and after extrusion. The in vitro protein digestibility increased from 77 to 81% for chickpea and 73 to 76% for maize; values for sorghum remained at 74% after extrusion. However, the IV-PDCAAS for the extruded flours generally remained at the same level, 69% for chickpea, 22% for sorghum, and ∼35% for maize. The effect of extrusion temperature, moisture and their interaction was significant on protein quality of sorghum and maize, but in the case of chickpea, only the extrusion temperature was significant. Only chickpea extruded at 150 ℃ (regardless of the moisture) met the protein quality (PDCAAS > 70%) requirement to be used in food assistance products.