Study of antioxidant activity and phenolic compounds of extracts obtained from different craft beer by-products

This work deals with the study of the in vitro antioxidant potential of aqueous extracts obtained from brewer's spent grain (BSG) and lees (BL) from four brewing craft beers. The effect of type of malt (base malts with different percentage of roasted malt (BSG1: 0%, BSG2: 7,2%, BSG3: 11,8% and BSG4: 16%) and hop added during brewing (BL1-3: boil hopping, BL4: boil and dry hopping)) on the antioxidant potential of extracts, was studied. Results for BSG showed that the higher the content in roasted malt, the lower DPPH, ABTS+ and TPC values were found in BSG extracts. Results for BL extracts showed that BL4 (boil and dry hopping) presented the highest TPC content. Gallic acid, 4-hydroxyphenil acetate, epicatechin and sinapic acid were the major compounds contributing to the total phenolic content in all BSG samples whereas large differences among groups were found regarding to these compounds for BL.