Influence of enzyme treatment approach on the phenolics content and antioxidant potential of sorghum grain samples

Enzyme-assisted extraction of phenolics was performed from commercial broom, and GK Emese and Farmsugro 180 hybrid sorghum grain residues with cellulolytic and esterolytic cocktails of Rhizomucor miehei NRRL 5282, Gilbertella persicaria SZMC 11086 and Mucor corticolus SZMC 12031 fungi. Results showed an increasing tendency for total phenolic content (TPC) during incubation that was in a positive relation with total flavonoid content (TFC) for most treatments. Best TPC and TFC yields were obtained on broom sorghum with maximal values of 256.9 ± 11.7 mg gallic acid equivalent (GAE)/100 g dry matter (DM) and 159.4 ± 6.8 mg catechin equivalent (CE)/100 g DM, respectively, achieved during R. miehei enzyme treatment. Reducing power and radical scavenging activity assays demonstrated improved antioxidant activity for most treated samples that was in positive correlation (0.942 ≥ r ≥ 0.522) with the TPC and TFC variables. Chromatography analysis revealed hydroxybenzoates, i.e., protocatechuic, 4-hydroxybenzoic and vanillic acids, as major phenolics with yields ranging from 5.40 ± 0.57 to 132.85 ± 14.21 μg/g DM, but the content of hydroxycinnamates increased to a greater extent during the treatments. The enzyme treatments can be reliable methods for enriching phenolic antioxidants in sorghum substances utilizable in gluten-free food products.