ABSTRACT Melanoidins are high molecular weight compounds formed during the final stage of the Maillard reaction. Melanoidins have been studied in recent years because of their nutritional, biological and health implications, apart from their role on the stability during processing and shelf life of foods. A fast and robust microtiter plate-based assay for a quantitative screening of the antimicrobial activity of melanoidins was applied. Oxytetracyclin was used as reference for assessing the antimicrobial activity of different melanoidins isolated from model systems. The minimum inhibitory concentration was calculated, and activity was related to the antimicrobial activity of an oxytetracyclin solution (100 µg/L). Glucose–lysine melanoidin exerted the highest antimicrobial activity, being at a concentration of 1 mg/mL, equivalent to an oxytetracyclin solution of 170 µg/L.