Impact of extraction methods on protein functionality and nutritional quality of the Laird lentil (Lens culinaris Medik.) protein ingredients

Lentils are promising alternative crops for the protein industry due to their varietal diversity, protein composition, and abundant production. Lentil is the world’s third most-produced legume. Therefore, this study aims to extract protein with high purity and improved functionality from Laird lentils using a green and sustainable deep eutectic solvent (DES) system comprising choline chloride and glycerol. The extracted protein was characterized for physicochemical, functional, and protein quality parameters compared to alkaline, monovalent, and divalent salt-extracted protein isolates. DES extraction produced protein isolates with significantly higher protein content (96.04±0.16%, N×6.25) than all other protein extraction methods (P <0.05). The protein yield (58.45±0.46%) and protein recovery rate (17.71±0.14%) of DES-extracted protein were significantly higher than alkaline-extracted protein, while there were no significant differences in them among DES- and salt-extracted protein isolates (P<0.05). According to secondary structure analysis, α-helix (18.10%) and β-sheet (68.30%) contents in DES-extracted protein were higher than those of alkaline and salt-extracted protein. The molecular weight distribution pattern showed significant differences between protein isolates. DES-extracted protein had significantly higher emulsion activity, stability, and gelation properties than alkaline (P<0.05). Functional properties of DES-extracted protein were not mostly significantly different from those of monovalent and divalent salt-extracted protein isolates. In-vitro protein digestibility-corrected amino acid score (IV–PDCAAS) was significantly higher in DES-extracted protein (70.6±0.7%) compared to all other protein isolates (P<0.05). In-vitro, protein digestibilities (IVPD) of DES (84.2±0.8%), monovalent salt (83.4±0.9%), and divalent salt (84.1±1.1%) extracted proteins were not significantly different. DES extraction is a promising technique that could be an alternative to conventional protein extraction technologies to produce sustainable and high-purity protein ingredients from green lentils. This research will open up a new frontier in plant protein research and the utilization of proteins and co-products in various applications.