A proteomics–bioinformatics approach to assess the molecular and physicochemical properties of brewer's spent grain protein concentrates: Effect of alkali-heat treatment

Abstract

Brewer's spent grain (BSG) can serve as an attractive protein source due to its low cost and excellent nutritional and functional attributes. Alterations induced by protein extraction process in the BSG protein molecules can affect their functionality and nutritive value. This study investigated the effects of moderate heating during alkaline extraction on the molecular-physicochemical properties of BSG proteins. To this end, BSG protein concentrates were extracted at either room temperature or 50 °C, followed by proteomics and bioinformatics analyses. It was observed that the sample extracted at 50 °C contained proteins with a higher molecular weight, longer length, and enhanced stability relative to the sample extracted at room temperature. The content of acidic proteins showed a 14 % increase due to extraction at 50 °C. A simultaneous decrease in the content of both highly hydrophilic and highly hydrophobic proteins occurred in the sample extracted at 50 °C, while increasing the content of mildly hydrophilic proteins by approximately 25 %. This sample also contained a higher content of essential amino acids. Moreover, the content of proteins with a very high extinction coefficient (>50000 M−1cm−1) increased by 26 % due to extraction at 50 °C. Overall, these findings demonstrate that moderate heating during alkaline extraction can modulate the physicochemical and molecular properties of BSG proteins, providing insights into tailoring their functionality for specific industrial applications.

Keywords

• Protein molecular weight
• Hydrophobicity
• Instability
• Amino acid composition