Valorisation of green lentil waste flour into protein concentrates by ultrafiltration for plant-based food applications

The increasing demand for sustainable protein sources and the urgent need to reduce food waste have driven interest in valorising legume side streams. This study aimed to develop a high-protein concentrate from green lentil waste flour (LWF) using ultrafiltration (UF). Proteins were recovered via alkaline extraction, centrifugation, followed by UF, whose performance was assessed in cross-flow mode using a 100 kDa molecular weight cutoff. The resulting protein-rich retentate, at a Volume Concentration Ratio (VCR) of 6.00, was evaluated for its composition, physicochemical characteristics, protein profile, and functional properties as a gelling ingredient. A retentate containing ~16 % protein (~80 % of total solids), enriched in globulins and albumins, as confirmed by SDS-PAGE and FTIR, was produced by UF. Colour and ζ-potential analyses confirmed the concentration and retention of proteins and colloidal stability. The retentate exhibited viscoelastic gel-like properties with a gelling point at 72.5 ◦C, a mild overshoot in G″ beyond the linear viscoelastic region, high water-holding capacity (96.5 %), and a hardness of ~145 g, indicating potential for use as a structuring agent. These findings demonstrate the technical feasibility of ultrafiltration in recovering functional proteins from lentil side streams, thereby contributing to circular economy goals and plant-based food innovation.