ENERGY CONSUMPTION IN SINGLE‐SCREW EXTRUSION PROCESSING OF FULL FAT AFRICAN BREADFRUIT (TRECULIA AFRICANA) BLENDS

Abstract

ABSTRACT Full fat African breadfruit, corn and defatted soy blends with moisture content range of 6.20–7.50% (wet basis) were extruded in a single‐screw Brabender laboratory extruder (DCE 330, Brabender Instruments Inc., South Hackensack, NJ) at varying independent process variables of feed composition (fc), feed moisture (fm) and screw speed. A central composite design was employed to study the effects of these variables and extrusion cooking on several quality characteristics of the center point blend, and energy input as torque and specific mechanical energy (SME). SME is relevant in that the more the energy applied, the greater the degradation of starch while torque is directly correlated with power usage. Extrusion cooking significantly (P ≤ 0.05) affected bulk density, water absorption, water solubility and nitrogen solubility indices. Torque and SME ranged from 4.00 to 8.50 N·m and 216 to 376 kJ/kg, respectively. Regression analysis of data generated of experimental data showed that fc had significant (P ≤ 0.05) quadratic effect on both energy measurements. Screw speed and fm showed significant (P ≤ 0.05) linear effects on SME while screw speed alone showed significant (P ≤ 0.05) linear effect on torque. At 160‐rpm screw speed and 85% fc, the torque value was maximum (8.50 N·m). Maximum SME value of 376.72 kJ/kg was obtained at 85% fc, 24% fm and 120‐rpm screw speed. Economically, therefore, extruded products made from blends of breadfruit, corn and soy flours will require lower extruder power usage given the fat and fm levels. Findings of this research might be useful to processors for better process control and optimal energy utilization when extruding these or related blends in a single‐screw extruder.