Proteolytic enzymes positively modulated the physicochemical and antioxidant properties of spent yeast protein hydrolysates

Abstract

The spent brewer yeast (SBY) is a by-product with great potential for the production of peptides. Protein hydrolysates of SBY with improved physicochemical and antioxidant properties were produced by a system containing mixtures of proteases (Alcalase™, Brauzyn® and Protamex™). The amount of solids and crude proteins recovered from the raw material after the protein hydrolysis was, in average, 57% and 70% (w/w), respectively. Hydrolysis resulted in intermediate degrees of hydrolysis (15%), promoting the release of hydrophobic residues (8% higher related to the control) with antioxidant properties. The presence of all three enzymes influenced the degree of hydrolysis but the darkening and browning of the hydrolysates were mainly affected by Protamex™. Most of the hydrolyzed proteins presented a molecular weight (MW) of 35 kg mol-1, as confirmed after membrane separation and electrophoresis. The membrane fractionation step using 30 kg moL-1 membranes effectively produced peptide-enriched fractions of 30-35 kg moL-1. In addition, it was possible to correlate the degree of hydrolysis, solids release, color parameters L*, Browning Index and antioxidant properties by FRAP and DPPH in function of the hydrolysis conditions, showing the potential use of SBY protein hydrolysates as a source of peptides in value-added functional foods.