Biocatalytic Degradation of Proteins and Starch of Extruded Whole Chickpea Flours

Abstract

In this study, the effects of extrusion cooking of whole chickpea flour in preparation for its further hydrolyses with proteases and amylases were evaluated. The thermoplastic extrusion process was carried out varying processing moisture (15.6% or 22.55%), final barrel temperature (143°C or 150 °C), and screw speed (450 rpm, 580 rpm, or 700 rpm) to generate three specific mechanical energy (SME) inputs (127.95 Wh/kg, 161.58 Wh/kg, and 199.13 Wh/kg). After extrusion, flours were hydrolyzed with alcalase and α-amylase in order to maximize soluble compounds after hydration. In general, extrusion did not affect chemical composition but caused structural modifications that influenced functional properties and in vitro protein and starch digestibilities. Extruded chickpea flours presented higher content of soluble proteins and increased starch hydrolysis after alcalase and α-amylase treatment, respectively. It was found that extrusion treatment of chickpea with a SME input of 127.95 Wh/kg produced at 22.5% processing moisture, 150 °C of final temperature, and 580 rpm of screw speed in combination with the later alcalase/α-amylase treatments achieved the highest degree of starch hydrolysis (84%) and the release of both soluble proteins (70%) and total soluble solids (62%). These results suggest that amylolytic and proteolytic digestion combined with the extrusion process could transform the whole chickpea flour into a valuable soluble food ingredient with adequate contents of proteins and starch-derived dextrins and sugars.