Sustainable production of low molecular weight phenolic compounds from Belgian Brewers' spent grain

Abstract

Brewers' spent grain (BSG) is a brewery co-product rich in phenolic compounds which only within Europe, 3-4Mt is generated annually. This study aims to sustainably isolate low-molecular-weight phenolic compounds from Belgian BSG using a microwave-assisted method (MW). Two types of BSG (from light and red malted barley grains) were subjected to MW at 600 and 800 W for 5, 15 and 30 min. MW showed a significant and positive effect on the release of 4-vinylguaiacol, a bioactive compound derived from the thermal decarboxylation of ferulic acid. The amounts of 4-vinylguaiacol in the extracts increased by about 80% after 30 min of MW despite the power applied. In the same time interval, total phenolic contents (TPC) increased of about 70% for light and 60% for red BSG. The highest TPC (13.23 mg/gDM) was obtained at 30 min and 600 W. This sustainable method could help add value to BSG by improving the extractability of bioactive phenolics.