Protective ability against oxidative stress of brewers' spent grain protein hydrolysates

The protein fraction of Brewers' spent grain (BSG) was used as substrate to obtain hydrolysates with antioxidant activity. Three enzymatic approaches were applied: brewer's spent yeast (BSY) proteases, Neutrase® and Alcalase®, at the same proteolytic activity (1U/mL), using an enzyme/substrate ratio of 10:100 (v/v), at 50°C, 4h. Total Phenolic Content (TPC) and Ferric Ion Reducing Antioxidant Power (FRAP) of hydrolysates and fractions <10kDa and <3kDa were assayed. Additionally, the protective ability of <10kDa fractions against oxidative stress on Caco-2 and HepG2 cells was investigated. Alcalase® hydrolysate presented significantly (p<0.05) higher TPC and FRAP (0.083mgGAE/mgdw; 0.101mgTE/mgdw, respectively) than Neutrase® and BSY hydrolysates. The three BSG protein hydrolysates (fraction <10kDa) exerted protective effect against free-radical induced cytotoxicity in Caco-2 and HepG2 cell lines, but the strongest effect was observed for BSY hydrolysates, therefore, it presents greater potential as functional ingredient.