Microbial contamination in alcoholic fermentation is a widespread concern. Antibiotics are generally used for controlling bacterial contamination. However, drug-resistant strains and some health restrictions have limited the use of antibiotics. Here we propose the addition of hop extract as a natural antibacterial agent in alcoholic fermentation processes. Besides the behavior of the hop extract and the biocide Kamoran (R) were compared. The simultaneous evaluation of yeast, hop extract and bacterial concentrations as experimental variables enabled us to determine optimal conditions for contaminated fermentation processing. We determined that the optimal yeast and hop extract concentrations are 35 g L-1 and 46 mg L-1, respectively, and the bacterial concentration does not significantly influence the analysis. The use of the natural hop extract presents similar results to the biocide Kamoran. (C) 2012 Elsevier B.V. All rights reserved.