How do pH and temperature influence extraction yield, physicochemical, functional, and rheological characteristics of brewer spent grain protein concentrates?

In this study, brewer spent grain (BSG) proteins were obtained by one-stage alkaline extraction and the influence of extraction pH and temperature on protein extraction yield, physicochemical, functional, and rheological characteristics were assessed. Under the optimized conditions (pH 11, 60 °C and solid/solvent ratio of 1/17 g/mL), up to 87% of the proteins were extracted. Mild alkaline (pH 8) extraction resulted in extracts with higher protein content (>40%) that were more soluble and with better emulsifying properties compared to extraction at extreme alkaline conditions (pH 11 and 12). Increasing the extraction pH to 11 or the temperature to 80 °C resulted in BSG protein concentrates (BSG-PCs) with lower protein content (∼30% protein) (p < 0.05) and slightly less soluble. However, the BSG-PCs obtained under more severe conditions presented the largest increases in G’ and G” during the temperature sweep test, indicating that the changes caused by the process could have improved the gelling properties of these proteins. BSG-PC is a promising plant protein that could be used as an alternative for the development of different food products.