Process optimization of extrusion process variables for improving the quality and extrudate characteristics of wheat-tiger nut pasta

Abstract

Tiger nuts are underexploited crops with essential potential that remains untapped with capability to be a better alternate for wheat flour in pastry industries. This research evaluates the effect of extrusion variables on the quality and extrudate characteristics and sensory acceptability of wheat-tiger nut pasta. Tiger nut flour was substituted with wheat flour at 0, 10 and 20%. A Box-Behnken experimental design with three independent variables; feed composition (80:20, 90:10 and 100:0%), moisture content (5, 10 and 15%, wb) and barrel temperature (60, 70 and 80 °C) were used and these resulted in a total of 17 experimental carried out to produce extruded pasta. Results showed that feed composition enhances and increased the ash, protein, fibre and carbohydrate contents of the pasta, while increase in barrel temperature resulted in low fat content. High feed composition and low feed moisture content resulted in high bulk density, water and oil absorption capacities and swelling capacity of wheat-tiger nut pasta. The residence time, mass flow rate and expansion ratio progressively increased with a rise in feed composition, feed moisture content and barrel temperature. The responses models gave good fit with R2> 0.90, which indicate the adequacy of the models to predict closely the experimental data. However, the optimization of combined effects of extrusion variables was achieved with 80% wheat and 20% tiger nut flour containing 15% feed moisture content extruded at 70 °C temperature. These variables are critical in commercial production of improved high quality wheat-tiger nut pasta.