Antimicrobial Activity of Microgard™ Against Food Spoilage and Pathogenic Microorganisms

Abstract

Microgard™, a commercially available fermented milk product containing antimicrobial metabolites, was a potent inhibitor for Gram-negative bacteria such as Pseudomonas, Salmonella, and Yersinia when 1% concentration was incorporated into agar media. Gram-positive Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes were insensitive to Microgard™. Kluyveromyces marxianus, an unidentified black yeast, and Penicillium expansum were partially suppressed, whereas Aspergillus niger and a yogurt spoilage yeast were tolerant to 5% Microgard™. Optimum activity of Microgard™ was at pH 5.3 and below; the concentration that gave complete inhibition depended upon the number of bacteria present as well as the genus tested. Blood agar base reversed the antagonistic activity of Microgard™ against Pseudomonas putida compared with plate count agar. © 1991, American Dairy Science Association. All rights reserved.