Effect of soaking and extrusion on functional and pasting properties of cowpeas flour

Abstract

Cowpea (Vigna anguiculata) is a leguminous crop that is widely grown and consumed in Asia and Africa as a major source of dietary protein. This study investigated the effect of varying extrusion conditions (temperature and moisture content) on the functional and pasting properties of cowpea flour. Particle size distribution, functional and pasting properties of cowpeas flour were determined. Moisture content had a significant effect on the functional and pasting properties of cowpeas flour followed by temperature. Increasing moisture content from 10% to 15%, increased the bulk density from 0.4 to 0.5, Oil Absorption Capacity 149 to 238, Water Absorption Capacity 407 to 422, Swelling Power 4.6 to 4.9, Water Absorption Index 3.9 to 4.2, as well as Peak & Breakdown viscosities. On the other hand, reducing the moisture content decreased Water Solubility Index (WSI) from 31 to 21. Lower extrusion temperature increased all the functional properties except WSI along with pasting properties namely Peak, Final and setback viscosities. Higher extrusion temperature increased WSI, breakdown, peak time, and pasting temperature. The results suggest that variation of extrusion conditions can be used to modify the functional and pasting properties of cowpea flour to suit different applications.