Extrusion processing of unripe banana and defatted peanut flours: Effect of process variables on physical and machine parameters

The study aimed to develop nutritionally enriched extruded products using unripe banana flour (UBF) and defatted peanut flour (DPF) through optimization of extrusion parameters. UBF, rich in resistant starch and bioactive compounds and DPF, high in protein and low in fat, were selected as base materials. A Central Composite Rotatable Design (CCRD) under Response Surface Methodology (RSM) was employed to examine the effects of feed moisture content (12-18%), screw speed (200-300 rpm) and die head temperature (90-150 °C) on machine responses (torque, mass flow rate) and physical properties (bulk density, specific length, expansion ratio). Experimental results showed that torque ranged from 15-23 Nm, mass flow rate from 135-170 g/min, bulk density from 0.043-0.066 g/cm³, specific length from 91.11-171.95 mm/g and expansion ratio from 2.13-3.29. Feed moisture, screw speed and die head temperature significantly influenced these responses, with higher screw speed and lower moisture enhancing flow rate, elongation and expansion while reducing bulk density. Regression models were significant (R² = 0.84-0.99) with non-significant lack of fit, confirming model adequacy. Optimization suggested ideal conditions at 13.21% feed moisture, 270 rpm screw speed and 117 °C die head temperature. Validation under these conditions showed close agreement between predicted and experimental values with minimal deviations: torque (16.30 Nm), mass flow rate (162.01 g/min), bulk density (0.040 g/cm³), specific length (175.32 mm/g) and expansion ratio (3.01). The findings demonstrate that UBF-DPF blends can be effectively processed into extruded snacks with desirable physical qualities, enabling value-added utilization of underutilized resources and supporting the development of protein-and fiber-rich ready-to-eat products.