Structuring dry-fractionated faba bean protein concentrate using a micro-compounder: Effects of moisture, heat and salt addition

Dry-fractionated pulse protein concentrates are emerging as promising ingredients for the texturisation of plant-based foods, offering a cost-effective and environmentally sustainable alternative to wet-extracted proteins. However, their rheological behaviour under extrusion-relevant conditions remains underexplored. This study demonstrates the use of a micro-compounder, which is a benchtop co-rotating twin-screw extruder suitable for small sample volumes (>15 mL) to process dry fractionated faba bean protein concentrate (FPC) under conditions mimicking high-moisture extrusion. The effect of barrel moisture content (50, 55 and 60 %), processing temperature (100, 110 and 120 °C), and salt addition (NaCl, KCl, CaSO 4 ) on melt viscosity, mechanical responses (shear stress, force and specific mechanical energy), protein secondary structure, microstructure, and water-absorption capacity (WAC) of the extrudate were evaluated. Processing at 55 % moisture and elevated temperatures (110–120 °C) reduced melt viscosity while maximising WAC and altering water mobility as confirmed by NMR relaxation measurements. FTIR analysis revealed processing-induced decrease in β-sheets (from 45 % to a minimum of 35–57 %), accompanied by an increase in unordered structures (from 17 % to a maximum of 18–31 %) especially at lower moisture content (50 %) and elevated temperatures (≥110 °C), and SEM confirming transformation from particulate to cohesive network structures of the samples. To the best of our knowledge, this represents the first systematic application of a micro-compounder to evaluate dry-fractionated pulse proteins, addressing a critical knowledge gap in understanding how native-state proteins respond to thermo-mechanical processing. These findings highlight the suitability of dry-fractionated pulse proteins in food application and demonstrate the micro-compounder as a valuable tool for evaluating plant protein functionality under extrusion-relevant conditions. • Micro-compounder enables testing of novel proteins under extrusion conditions. • Viscosity measurements of dry-fractionated faba bean protein under extrusion-relevant conditions. • Optimised processing conditions enhance protein network formation and WHC. • Salts increase water mobility but reduces water-holding capacity. • FTIR and NMR confirm processing-induced changes in protein secondary structure, SEM imaging reveals transformation of sample surface structure.