High Hydrostatic Pressure-Assisted Extraction Enhances Protein Recovery and Techno-Functional Properties of Brewer’s Spent Grain Protein Isolate

Abstract

Brewer’s spent grain (BSG) is a major by-product of brewing industries and a potential protein source for valorisation. Conventional protein extraction methods often yield low protein recovery and poor techno-functional properties due to the rigid fibre matrix of the BSG. This study evaluated the effect of high hydrostatic pressure (HHP)-assisted BSG protein extraction (0.1, 300, 450, and 600 MPa) on protein extraction efficiency, structural modification, and techno-functional properties of BSG protein isolate (PI). Regardless of pressure, HHP-assisted extraction significantly enhanced protein recovery and purity of BSG PI compared to the control. Amino acid profiles also varied among different pressure levels, indicating the recovery of slightly different protein fractions. Major conformational changes were observed at 600 MPa, resulting in increased protein solubility. Free thiol content was unaffected up to 450 MPa but increased at 600 MPa compared with 300 and 450 MPa. In general, the emulsion activity index (EAI) decreased in all HHP-treated groups compared to the control except at 450 MPa, whereas the emulsion stability index (ESI) was unaffected. Foaming capacity (F0) remained unchanged, but foam stability (FS) increased three-fold at 600 MPa compared to the control. The least gelation concentration (LGC) was reduced to 7% in all HHP-treated BSG PI compared to the control (9%). Overall, current results showed that HHP-assisted extraction sustainably improves BSG PI extraction efficiency and induces structural changes that enhance most techno-functional properties, except for the EAI, supporting the use of BSG PI as a sustainable alternative protein ingredient.