Supercritical carbon dioxide extraction of brewer's spent grain

Brewer's spent grain (BSG) is the major by-product of brewing industry, produced in large quantities annually. Generally, it has been mainly used as feedingstuff but it was demonstrated that it contains a number of potentially high-value components. The aim of this work was to find proper supercritical fluid extraction (SFE) conditions to give bioactive compounds from BSG. The effects of three factors including pressure (15-35 MPa), temperature (40-60 degrees C) and CO2 + ethanol (0-60% ethanol concentration, v/v) were investigated. Among the extraction variables, the best conditions were found considering the criterion of maximum concentration of phenolic compounds (0.35 +/- 0.01 mg/g BSG), flavonoids (0.22 +/- 0.01 mg/g BSG) and antioxidant potential, evaluated by the ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical (2.09 +/- 0.04%/g BSG): 35 MPa of pressure, 40 degrees C of temperature and CO2 + 60% ethanol (v/v). (C) 2015 Elsevier B.V. All rights reserved.