Co-extrusion of food grains-banana pulp for nutritious snacks: optimization of process variables

Optimization, modeling, and characterization study for the physicochemical properties of raw banana and defatted soy composite extrudates

Novel raw banana and defatted soy composite extrudates were formulated to combat celiac enteropathy. The influence of four independent parameters viz. barrel temperature (BT: 60-80 °C), screw speed (SS: 200-300 rpm), moisture content (MC: 10-20%, wb), and defatted soy flour content (SFC: 0-32%) on physicochemical properties of extrudates were evaluated. Response surface methodology (RSM) identified the optimum extrusion conditions (80 °C BT, 200 rpm SS, 10% MC, and 32% SFC). Compared to RSM (R²:0.379-0.918), artificial neural network (R²:0.909-0.991) proved as a better tool for response prediction. Scanning electron microscopy confirmed the antagonistic effect of SFC addition on extrudate porosity. The addition of SFC decreased the crystallinity of the starch granules (71 to 49%), whereas, storage time had a positive effect (49 to 53%) on crystallinity of the composite extrudates. Fourier transform infrared spectroscopy analysis elucidated the secondary structures of protein in the composite flour which were degraded during the extrusion cooking.