Antimicrobial Activity of Microgard^TM Against Food Spoilage and Pathogenic Microorganisms

¹ Department of Food Science and Technology
² College of Pharmacy
³ Department of Microbiology, Oregon State University, Corvallis 97331-3804

Microgard^TM, 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^TM. 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^TM. Optimum activity of Microgard^TM 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^TM against Pseudomonas putida compared with plate count agar.

Key Words: Microgard^TM • pathogens • antimicrobial activity

Submitted on April 16, 1990
Accepted on September 28, 1990

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