Evaluation of the technological functional properties and antioxidant activity of protein hydrolysate obtained from brewers' spent grain

Abstract

Beer production generates a large amount of waste, called brewers' spent grain (BSG), which has a nutritional potential mainly as a protein source. Proteins can be modified by hydrolysis releasing peptides with different bioactivities, such as antioxidant activity. The aim of this study was to produce a protein hydrolysate from protein concentrate obtained from BSG, evaluating its functional properties and antioxidant activity. The BSG protein concentrate was obtained by changing the pH at the isoelectric point, established at 3.5. The concentrate was hydrolyzed with the enzyme Alcalase, after defining the enzyme: substrate ratio (2:100), and 4 h was hydrolysis time (hydrolysis degree 32%). The hydrolysate showed better results of antioxidant activity than the concentrate in all tested methods, highlighting the ABTS radical capture with activity above 90%. The foaming capacity was not significantly modified (49%–45%), while emulsion capacity was significantly improved (30%–72%) by the hydrolysis process. Practical applications The results of this work indicate that some functional properties of BSG can be upgraded by enzymatic hydrolysis. These BSG hydrolysates showing improved antioxidant and emulsifying activities can be useful ingredients in food formulations adding value to this important byproduct of the beer industry.

Extraction, Composition, Functionality, and Utilization of Brewer’s Spent Grain Protein in Food Formulations

“…Thus, untreated BSG showed rather inferior emulsifying properties compared to other protein materials, and for this reason, other authors investigated the emulsifying properties of hydrolyzed BSG proteins ( Table 5 ). In most studies, a protein extract was prepared using a single alkaline extraction or it was combined with ethanol or reducing agents to enhance the protein extraction yield [ 36 , 72 , 76 , 89 ]. These protein extracts were subsequently treated using different proteases.…”

“…One study also treated the BSG before extraction with Rhizopus oligosporus [ 72 ]. However, in each case, the hydrolysis increased the EAI compared to the untreated protein extract [ 36 , 71 , 72 , 76 , 89 ].…”

“…The increased foam forming capabilities were related to particle formation due to associative complexation and an optimum balance of negative charges as well as hydrophobicity, which positively influenced film formation and thus foam stability. Celus et al [ 36 , 89 ], Naibaho et al [ 62 ], Connolly et al [ 71 ], Vieira et al [ 76 ], and Chin et al [ 72 ] investigated how enzymatic/fungi hydrolysis affects the foaming ability of BSG proteins. Protein extraction generally enhanced the ability to form and stabilize foams, and hydrolysis further enhanced these capabilities in most studies ( Table 5 ).…”

“…Especially alcalase and pepsin have been shown to efficiently improve the foaming properties up to a degree of hydrolysis of 2–4% [ 36 ]. Higher degrees of hydrolysis typically decreased the foamability and foam stability [ 36 , 76 ].…”

“…Celus et al [ 36 , 89 ], Naibaho et al [ 62 ], Connolly et al [ 71 ], Vieira et al [ 76 ], and Chin et al [ 72 ] investigated how enzymatic/fungi hydrolysis affects the foaming ability of BSG proteins. Protein extraction generally enhanced the ability to form and stabilize foams, and hydrolysis further enhanced these capabilities in most studies ( Table 5 ).…”