Valorization of brewing by-products: obtaining flavor-enhancing and antioxidant compounds from spent yeast

Abstract

This study optimized the recovery of flavor-enhancing and antioxidant compounds from brewing spent yeast using a two-factor (autolysis time and temperature) response surface design. Chemical composition, sensory attributes, and in vitro antioxidant activity were evaluated. Optimization aimed to maximize umami flavor, pungency, and antioxidant properties, while minimizing bitterness and yeast odor. Autolysis time strongly influenced free glutamic acid and glucose, with longer durations increasing their levels. Both time and temperature affected protein hydrolysis (PH), peptide hydrophobicity, phenolic compounds (e.g., protocatechuic and chlorogenic acids), and bioactives such as GABA and taurine. Longer autolysis enhanced umami taste, whereas shorter durations improved antioxidant activity (ABTS+, DPPH, FRAP) and reduced copper-chelating capacity. Significant correlations (p < 0.05) linked composition to functionality, including bitter taste with protein hydrolysis, umami with glutamic acid, ABTS with chlorogenic acid, and copper-chelating activity with PH or amphipathic peptides. These findings show that autolysis conditions can be strategically tailored to target specific sensory and bioactive profiles, offering a practical approach to valorize spent yeast as a functional ingredient for food applications.