In vitro protein digestibility of direct‐expanded chickpea–sorghum snacks

Abstract

AbstractBlending cereals with pulses provides a balanced protein with higher biological value as their amino acid compositions are complementary. Extrusion not only can improve protein digestibility but also may reduce essential amino acid content. This study investigated the effects of extrusion parameters and blend ratio on in vitro protein digestibility (IVPD) and IVPD‐corrected amino acid score (IVPDCAAS) of direct‐expanded chickpea–sorghum snacks. Chickpea–sorghum blends (50:50, 60:40, and 70:30 chickpea:sorghum, w/w) were extruded at 10 combinations of moisture content (16%, 18%, and 20%) and barrel temperature (120°C, 140°C, and 160°C), and at 169°C and 15% moisture, the conditions identified in a previous study as producing maximal expansion. Chickpea and sorghum flours were extruded at 140°C and 18% moisture for comparison purposes. The IVPD of raw 50:50, 60:40, and 70:30 chickpea–sorghum blends ranged from 76% to 78%; values for raw chickpea and sorghum flours were 79% and 74%, respectively. Extrusion increased IVPD (P < 0.05) of all flours and blends. An increase in extrusion temperature increased the IVPD of extrudates (P < 0.05), whereas an increase in moisture content had the opposite effect (P < 0.05). The IVPDCAAS of raw 50:50, 60:40, and 70:30 chickpea–sorghum blends were 0.64, 0.72, and 0.73, respectively; values for raw chickpea and sorghum flours were 0.74 and 0.27, respectively. Extrusion increased IVPDCAAS (P < 0.05). The 70:30 chickpea–sorghum blend extruded at the maximal expansion exhibited the highest protein quality indicating this to be the optimal condition for snack production.