Antimicrobial Activity of Quinoa Protein Hydrolysate against Streptococcus pyogenes and Escherichia coli

Quinoa seed, as a rich source of protein with strong antioxidant properties, plays an important role in improving consumers’ nutrition. This study was aimed at comparing the antimicrobial activity of peptides from quinoa hydrolysed proteins (QHP) on Streptococcus pyogenes as a Gram-positive and Escherichia coli as a Gram-negative bacterium with gentamicin antibiotic as a positive control. Different enzymatic ratios of pepsin and alcalase (30–90 AU/kg protein) at different temperatures (50–55°C) and times (150–210 min) were used to determine the optimal conditions for peptide hydrolysis with the highest antimicrobial properties. Similar to gentamicin, the maximum growth inhibition zones were 11.88 ± 0.37 mm and 12.49 ± 0.58 mm for S. pyogenes and E. coli, respectively, with an enzyme/substrate ratio as 60 AU/kg protein, a peptides concentration of 800 μg/ml, and at 50°C for 150 min of hydrolysis. The results showed that QHP has a good inhibitory effect on the bacteria mentioned and can be used as a food preservative.