Unveiling the contribution of Osborne protein fractions to the physicochemical and functional properties of alkaline and enzymatically extracted green lentil proteins

Abstract

AbstractLentil proteins are gaining popularity as food ingredients, serving both functional and nutritional purposes. To better understand the properties of lentil proteins extracted using commercially relevant methods (alkaline and enzymatic), sequential fractionation by solubility (Osborne fractionation) was performed and the physicochemical, thermal, and functional properties of the extracts were characterized. Fractionation revealed that 43% of lentil proteins were water‐soluble (ALB, albumin‐rich), 37% salt‐soluble (GLO, globulin‐rich), 14% alkaline‐soluble (GLU, glutelin‐rich), and 3% ethanol‐soluble (PRO, prolamin‐rich). Protein extraction yields of 81% and 87% were achieved by alkaline (pH 9.0, 50 °C, 1:10 solids‐to‐liquid ratio, 60 min) and enzymatic extraction (same conditions with 0.5% (w/w) Alkaline Protease), respectively. Proteomic analysis allowed for the identification of 129 proteins among all extracts, and the ALB and GLO fractions exhibited similar protein profiles as the alkaline‐extracted proteins. The secondary structure of the protein fractions was dominated by β‐sheets (20%–35%) and unordered structures (45%–48%). Surface hydrophobicity and absolute zeta potential were negatively correlated (R2 = 0.82, p < 0.05). ALB and GLO fractions had higher denaturation temperatures than the alkaline/enzymatically‐extracted proteins, potentially due to partial denaturation. ALB and GLO fractions also had the highest solubility and emulsification capacities. Under acidic conditions, enzymatically‐extracted proteins exhibited better solubility (58 vs. 33%), emulsification (499 vs. 403 g oil/g dry sample), and similar foaming capacity (57%–69%) compared to alkaline‐extracted proteins. This study showed that alkaline and enzymatically extracted lentil proteins share physicochemical and functional characteristics with water‐ and salt‐extracted proteins, demonstrating the efficacy of these single‐stage extraction strategies in achieving high yields and desirable functionality.