Optimization of lentil protein extraction and the influence of process pH on protein structure and functionality

•Lentil protein extraction was optimized to maximize both protein content and yield.•Partial protein hydrolysis and denaturation occurred when extracted at alkaline pH.•Both extraction and environmental pH could affect protein functionalities.•Lentil protein showed strong foaming capacity, comparable to whey and egg protein.

Response surface methodology was used to optimize alkaline extraction of protein from lentil flour to maximize both protein content and yield. Solid/solvent ratio and pH were the significant factors that determined protein extraction efficiency. At the optimized condition of pH 9.0 and solid/solvent ratio of 1:10 (g:mL), a yield of 14.5 g of protein extract/100 g of flour was obtained with a protein content of 82 g/100 g at (22 °C) after 1 h of extraction. The impact of extraction pH on the molecular structures and functionalities of lentil protein was investigated. Increasing the extraction pH to 10 caused partial protein hydrolysis and unfolding as suggested by size exclusion high performance liquid chromatography and Fourier transform infrared spectroscopy analysis, leading to improved protein solubility and gelling property. Environmental pH influenced protein solubility and surface charge, and subsequently the gelling and foaming properties. The foaming capacity was especially strong, comparable to whey and egg proteins.