Extracting proteins from Brewers’ spent grain using emerging technologies: Evaluating efficiency and use as emulsifier

Brewers’ spent grain (BSG) is the main side-stream of the brewing industry with an annual production of 40 million tons of wet weight. BSG has a protein content of 15-30 % dry basis, which makes it an interesting material for protein extraction. Normally, extraction is performed under high temperatures or high alkaline conditions. In this study, microwave-assisted extraction, pulsed electric field, ultrasound, and ohmic heating were tested to extract proteins from BSG without pH adjustment (pH 6) or at pH 9. The extracts were further tested for their emulsifying activity. The results obtained showed that the use of ultrasound at pH 9 resulted in the highest protein content and protein recovery of 24.1 % and 58.6 %, respectively. Extracts produced from microwave-assisted extraction and ohmic heating could produce the smallest emulsion droplets; however, the stability of all emulsions was low. The present study highlights the potential of emerging technologies as an alternative to harsh solvent usage in order to extract BSG proteins.