Development of antioxidant peptides from brewers’ spent grain proteins

Brewers' spent grain (BSG), the most abundant brewing by-product contains up to 24% (w/w) of protein on a dry basis but is used as low-value animal feed. This study was conducted to develop antioxidant peptides from BSG proteins. Protease hydrolysis significantly increased BSG protein solubility to 94.4% at neutral pH. Peptides prepared by Alcalase, and its combination with Neutrase, Flavourzyme, or Everlase showed the highest DPPH radical scavenging activities ranging between 72.6 and 74.9%. The highest superoxide radical scavenging activity of 19.3% was observed in the hydrolysate resulted from Alcalase and Flavourzyme combination. Everlase and FoodPro PHT combined treatment was the most effective in producing ferrous ion chelating peptides. Molecular structures analysis suggests that histidine significantly contributed to DPPH radical scavenging activity of BSG peptides due to the high proton donation ability of its imidazole ring. Highly hydrolyzed BSG protein could have more positive charges to stabilize negatively charged superoxide radicals. Ferrous ion chelating ability was negatively correlated to degree of hydrolysis, suggesting that longer peptides are more likely to form compact structures to trap ferrous ions. This research has demonstrated the potential to use BSG as a cost-effective raw material to generate natural antioxidants for food applications.