Extraction Condition–Driven Changes in the Techno-Functional and Thermal Properties of Protein Isolates From Underutilized Lupine (Lupinus spp.): Implications for Food Applications

Abstract

Lupine, an underutilized legume with high protein content, offers a promising plant-based protein source for functional foods. This study evaluated four lupine genotypes to determine how extraction pH (EpH) and isoelectric precipitation pH (IEPpH) influence the techno-functional and thermal properties of lupine protein isolates (LPIs) using response surface methodology (RSM) based on a central composite design (CCD). LPIs exhibited genotype-dependent functional behavior: Vitabor showed the highest solubility (95.9%–95.7%) at pH 7–9 and superior foaming capacity (240%) with stability of 89.2%; the local genotype excelled in emulsifying capacity (50%) and gelation (8%), and Probor had the highest oil holding capacity (2.96 g/g). Thermal analysis revealed Sanabor possessed the highest enthalpy (ΔH = 87.36 J/g) and broad denaturation range (Td = 82.5°C, Te = 122.8°C), indicating robust structural integrity, while the local genotype showed comparable thermal stability. Optimal EpH and IEPpH were genotype-specific, reflecting inherent compositional differences affecting protein functionality and thermal behavior. Based on their distinct profiles, LPIs from Local are suitable for dairy alternatives and meat analogues, Vitabor for protein-enriched beverages, and Probor and Sanabor for sauces, spreads, and heat-processed foods. These findings demonstrate lupine's versatility as a functional plant protein and provide mechanistic insight into how genotype and extraction conditions govern structural and functional performance. Future studies should investigate protein digestibility, bioactive peptide formation, and application in real food and industrial systems to fully harness the nutritional and functional potential of LPIs.