Optimization of protein extraction from brewer's spent grain and production of bioactive peptides

Brewers' spent grain (BSG), the major brewing by-product, is a rich source of proteins. However, the color and low solubility of BSG proteins (BSGP) are two main challenges that have restricted its application in food formulations. The objective of this study was to overcome these challenges via enzymatic hydrolysis of BSGP. In this approach, proteases from several origins were used, including Alcalase (bacterial), flavourzyme (fungal), papain (plant), and pancreatin (animal). Moreover, the evaluation of techno-functional and bioactive properties of BSGP hydrolysates was another part of this study. A response surface methodology (RSM) was applied for the optimization of BSGP extraction through the alkaline method. Extraction in optimized conditions, i.e., 2.12 h, 79.61 degrees C, and 67.52% H2O2, resulted in the highest extraction yield (28.18%) and lightness (66.89) which allowed a protein recovery of 64.53%. The highest solubility in neutral pH (47.56%) and water absorption capacity (3.87 (g/g)) were found for pancratin hydrolysate. The highest emulsion capacity was also related to pancratin hydrolysate, with emulsifying activity index = 84.98 (m(2)/g) and emulsifying stability index = 76.63%, respectively. The Alcalase hydrolysate showed the strongest scavenging activity against ABTS (IC50 = 1.7 +/- 0.08 mg/mL) and DPPH radicals (IC50 = 2.47 +/- 0.07 mg/mL), while flavourzyme hydrolysate had the best alpha-glucosidase inhibitory (IC50 = 9.25 mg/mL). This research presents BSG as a low-cost protein resource for the production of enzymatic protein hydrolysates with enhanced techno-functional and bioactive properties.