Functional and nutritional properties of fava bean ingredients processed by extrusion

Abstract

This study investigates the functional and nutritional properties of fava bean ingredients (flour, starch and protein concentrates) processed by twin-screw extrusion at various specific mechanical energy (SME) levels (100-3300 kJ/kg). The impact of incorporating flaxseed powders (20-70 %) to enrich polyunsaturated fatty acids is also examined. The extrudates exhibit varied bulk densities (50-1500 kg/m³), lightness (L* 75-87) and cell wall morphologies. The analyses include water solubility, pasting and emulsifying properties, protein hydrolysis degree and trypsin inhibitor activity. Results show that starch-rich extruded ingredients exhibit increased water solubility and reduced pasting properties due to starch depolymerization, while protein-rich ingredients are less affected. Emulsions containing extruded ingredients exhibit larger droplet sizes (d_[4,3] = 13-200 μm) compared to those with non-extruded ones (d_[4,3] = 4-13 μm), probably due to reduced protein solubility and adsorption. Higher extrusion intensity decreases pasting and emulsifying properties but increases water solubility; higher protein content reduces functional properties. In vitro protein hydrolysis, evaluated using the INFOGEST method, ranges from 66 % to 84 % and was unaffected by extrusion. All extruded ingredients exhibit low trypsin inhibitor activity levels (< 5 mg/g). Flaxseed incorporation does not alter nutritional properties. Extrusion at low SME (< 500 kJ/kg) effectively structures protein ingredients while optimizing their functional and nutritional properties.