Purpose: This study aimed to determine the activity of 2 commercial natural antimicrobial products against several organisms including enteric pathogens, spoilage Bacillus spp. and Enterobacter spp., lactic acid bacteria and yeasts of concern to the food industry. Product A consisted of white mustard essential oil containing 4-hydroxybenzylisothiocyanate (4-HBITC) and Product B was derived from citrus.
Methods: Product A was added to bacterial and yeast cultures in broth to final concentrations of 250, 500 and 1000 ppm based on 4-HBITC and growth (CFU/ml) monitored for 48-72 h at 22°C by spread plating. Absence of live cells was verified by incubation in Dey-Engley broth for 24 h followed by spread plating. Product B (19.53 - 5,000 ppm) was tested for minimum inhibitory concentrations (MICs) against bacteria and yeasts at pH 7.0, 6.5 and 6.0 using a microbroth-dilution assay. Minimum lethal concentrations (MLCs) were determined by direct plating method.
Results: Product A significantly inhibited the growth of all organisms tested at 1000 ppm, and was most effective against Salmonella Enteritidis and Schizosaccharomyces pombe, which were not detected at 500 ppm after 48 h and at 250 ppm throughout the trial, respectively. Product B inhibited all organisms within the concentrations tested, but was most effective against Listeria monocytogenes, Staphylococcus aureus and Bacillus spp. with MICs of 156.25-312.5 ppm at all pHs tested.
Significance: The results suggest that the antimicrobials tested are effective against a wide range of pathogens and spoilage organisms and have the potential to be evaluated in food products for improving safety and/or increasing product shelf life.