The Effect of Extrusion Conditions on the Physicochemical Properties and Sensory Characteristics of Millet – Cowpea Based Fura

Abstract

A three-factor three level Response surface methodology central composite retortable design (CCRD) was adopted to study the effect of feed composition (X1), feed moisture content (X2) and screw speed (X3) on proximate compositin, amino acid and sensory evaluation during extrusion of pearl millet and cowpea flour mixtures for the purpose of fura production. The mean observed value of protein for the fura extrudates ranged from 11.2 – 16.8%. Analysis of variance indicates that linear and quadratic effects significantly (P<0.05) affected the protein content of fura extrudates as expected. The mean value of lysine for the extrudates ranged from 5.1 - 6.6g/100g protein and the methionine content ranged from 1.3 - 3.8g /100g protein. The regression models fitted to the experimental data showed high coefficients of determinants with R2 = 0.96, 0.94, 0.94, 0.85 and 0.80 for protein (CHON), carbohydrate (CHO), fat (FAT), ash (ASH) and water (HOH) respectively. The R2 = were 0.90, 0.85, 0.86, 0.92, 0.88, 0.85 and 0.93 for lysine, i/leucine, leucine, valine, methionine – cystine, threonine and tryptophan respectively. The coefficients shows good fit. The importance of process variables on system parameters and physical properties could be ranked in the following order: Feed Composition (X1)>Feed Moisture (X2)>Screw Speed (X3). The optimum values obtained for feed composition, feed moisture and screw speed are 36.5% cowpea level, 22.3% feed moisture content and 186.7 rpm respectively. The corresponding optimum values of lysine, protein content, expansion ratio and bulk density are 6.6g/100g protein, 16.6%, 2.8 and 0.52 Kgm-3 respectively. The data obtained from the study could be used for control of product characteristics and possible projection for the commercial production of fura or any enriched protein based food from the blends pearl millet and cowpea.