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

- Brewers' spent grain protein hydrolysates present in vitro chemical antioxidant activity.
- Protein hydrolysates protected against oxidative stress in Caco-2 and HepG2 cells.
- Hydrolysates from Brewers' spent grain and spent yeast had strongest protective ability.
- A potential functional ingredient was obtained from two major brewing by-products.

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 (1 U/mL), using an enzyme/substrate ratio of 10:100 (v/v), at 50 °C, 4 h. Total Phenolic Content (TPC) and Ferric Ion Reducing Antioxidant Power (FRAP) of hydrolysates and fractions <10 kDa and <3 kDa were assayed. Additionally, the protective ability of <10 kDa fractions against oxidative stress on Caco-2 and HepG2 cells was investigated. Alcalase® hydrolysate presented significantly (p < 0.05) higher TPC and FRAP (0.083 mg GAE/mg dw; 0.101 mg TE/mg dw, respectively) than Neutrase® and BSY hydrolysates. The three BSG protein hydrolysates (fraction <10 kDa) 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.