Tailoring the functional and biological properties of lentil protein fractions through aqueous and enzymatic extraction process

Lentils are a rich protein source with rising popularity as a plant-based protein ingredient in food systems. The overarching objective of this work was to produce highly functional green lentil protein ingredients by investigating the effects of processing conditions on protein structure and functionality. Extraction conditions in the aqueous (AEP) and enzyme-assisted extraction processes (EAEP) were optimized using a holistic approach to enhance protein yields and functionality of the aqueous extract (concentrate). Screening of commercial enzymes and subsequent optimization using an experimental design led to the selection of pH 7.0, 1:21 solids-to-liquid ratio, and 60 min at 50 °C, with the addition of 0.5% Neutral Protease (EAEP only) as the best conditions, achieving 73.4% total protein extractability (TPE) for AEP and 80.9% for EAEP. Next, the effects of extraction scale-up (20 L), isoelectric precipitation (IEP), and spray-drying were assessed on the functionality of the curd (precipitate) and whey (acid-soluble fraction), compared to the concentrate. Scaled-up extractions achieved similar TPE (75.4% for AEP; 84.7% for EAEP) compared to lab-scale. Following IEP, 71.4% and 23.3% of the extracted proteins were recovered in the curd fraction for the AEP and EAEP, respectively. AEP and EAEP wheys were highly soluble in acidic and neutral conditions and exhibited consistently high foaming capacity (160 to 230%). Concentrates and curds exhibited minimum solubility near the isoelectric point. The EAEP curd and concentrate exhibited high foaming capacity at pH 3 and 4, but the EAEP decreased foaming stability among all fractions at most pHs. The EAEP curd achieved the highest emulsifying capacity (175 g oil/g protein) at pH 3, which could be explained by its higher surface hydrophobicity (1.9 x 10⁶). The results demonstrate that tailored extraction conditions leveraging controlled proteolysis, followed by protein fractionation can generate unique lentil protein ingredients with promising functional properties for food applications.