Understanding the impact of enzyme-assisted aqueous extraction on the structural, physicochemical, and functional properties of protein extracts from full-fat almond flour

The need for sustainable protein sources has prompted research on several plant-based protein matrices. The effects of enzymatic extraction on the composition, physicochemical, structural, and functional properties of protein-extracts (skim) from full-fat almond flour were elucidated. Protein-extracts were produced by aqueous (AEP), and enzyme-assisted extraction processes (EAEP), which enable concurrent extraction and fractionation of lipids and proteins without the use of flammable solvents. Except for the use of 0.5% of protease in the EAEP, extraction parameters were similar for both processes (pH 9.0, 50 °C, 1:10 solids-to-liquid ratio, and 60 min). The use of enzyme to assist the extraction resulted in the production of protein extracts with higher protein content and promoted the formation of smaller peptides and a more unordered protein secondary structure with reduced surface hydrophobicity. These structural modifications reduced the EAEP skim protein thermostability and improved its water absorption capacity (2.4 vs. 2.7 g water/g protein) compared with the AEP proteins. Importantly, proteolysis significantly enhanced the functionality of the hydrolysates at pH values close to the almond protein isoelectric point. At pH 5.0, EAEP skim proteins had higher solubility (47 vs 23%), emulsification capacity (492 vs 402 g oil/g protein), emulsification activity index (35 vs 17 m²/g) and foaming capacity (23 vs 11%) compared with AEP proteins. These results indicate that moderate hydrolysis can be used to improve extractability and the functionality of almond proteins, creating new opportunities for its application as food ingredients.