Lupin-based high-protein extrudates: Physicochemical, nutritional and techno-functional properties

Abstract

Lupin is an underutilized legume with high protein content (30–40 %) and strong potential for sustainable cultivation, but its use in the food industry is limited by the presence of anti-nutritional (saponins, alkaloids, polyphenols) and anti-technological factors, as well as suboptimal techno-functional properties. Low-moisture extrusion (LME) offers a promising strategy to overcome these limitations while producing high-protein texturized ingredients. In this study, five formulations combining lupin flour with laboratory or commercial lupin protein isolates were subjected to LME to evaluate effects on anti-nutritional compounds, techno-functional properties, and textural attributes. Extrusion reduced polyphenols (avg. 42 %), antioxidant activity (avg. 17 %) and saponins (avg. 47 %), while alkaloids remained stable. Water and fat absorption capacities were largely maintained (avg. 1.26 g water/g dm and 1.66 g oil/g dm, respectively), compared to powder formulations (avg. 1.31 g water/g dm and 2.25 g oil/g dm, respectively). Microstructural observations, along with bulk density (avg. 1.09 g/cm³) and texture analysis (average hardness of 346 N) confirmed the formation of compact high-protein extrudates (up to 88.6 % protein) and showed the effects of protein incorporation on matrix organization and textural properties, supporting their suitability as functional ingredients. Overall, this work demonstrates that LME can enhance the properties of lupin flour and isolates, producing high-protein extrudates with improved nutritional, functional, and structural qualities.