Effect of moderate heating during alkaline extraction on composition and functional properties of brewer's spent grain protein concentrates

Abstract

Brewer's spent grain (BSG) is a low-cost protein-rich residue and a valuable source of plant proteins. Extraction conditions and parameters can influence the composition and functionality of the resultant BSG protein concentrates. In this study, alkaline extraction at room temperature and 50 °C was investigated to explore the alterations induced by moderate heating in the composition, fatty acid and amino acid profiles, emulsion stability, and foaming properties of BSG protein concentrates. The protein content of the sample extracted at 50 °C decreased by 6%. An increase of 29.4% in the carbohydrate content and 2.5% in the lipid content was observed due to extraction at 50 °C. Hydrophobic amino acid content and saturated/unsaturated fatty acid ratio decreased by 20.9% and 4.8% respectively, in the protein concentrate extracted at 50 °C. Fourier transform infrared spectroscopy and gel electrophoresis showed some degree of protein structural modification and aggregation in the sample extracted at 50 °C. Although the heat-induced compositional alterations in the protein concentrate were not in favour of functionality, its emulsion stability and foaming capacity were significantly improved. These findings demonstrate that the heat-induced improvements in the surface hydrophobicity and conformational flexibility of proteins play a dominant role in the functionality of BSG protein concentrates. It can provide insights into modulating the performance of these valuable side-stream proteins for various food, pharmaceutical, and cosmetics products.