Melanoidins have been proposed as highly active against resistant microorganisms (Einarsson, Snygg, & Eriksson, 1983; Rufián-Henares & Morales, 2008; Stauder et al., 2010). Our results strongly suggest that a high content of melanoidins (Robusta coffee brew) is responsible for the growth inhibition of Gram-negative bacteria. Rufián-Henares and De la Cueva (2009) proposed that antimicrobial activity of melanoidins could be mediated by metal chelating mechanisms. Therefore, the complex mixture of compounds found in spent coffee (phenolic compounds, caffeine and melanoidins) is able to act as a suitable antimicrobial agent for extent food shelf-life, mainly against Gram-positive bacteria and yeast.