Antibacterial Effect of Wasabi against Listeria monocytogenes and Salmonella Typhimurium

Introduction: Listeria monocytogenes and Salmonella Typhimurium are two of the major bacterial pathogens frequently involved in foodborne outbreaks. Control of the two pathogens in foods especially Ready-to-Eat foods is essential to ensure food safety. It is of great interest in the use of antimicrobial compounds naturally present in edible plants to control foodborne pathogens. Wasabi (Wasabia japonica) is such an edible plant containing antimicrobial compounds.

Purpose: The purpose of this study was to evaluate the antibacterial effect of wasabi against L. monocytogenes and Salmonella Typhimurium.

Methods: Brain Heart Infusion (BHI) broth media supplemented with wasabi powder at varying concentrations were used in the study. The media were inoculated with fresh culture of L. monocytogenes or Salmonella Typhimurium to obtain the initial bacterial concentration approximately 10⁵ CFU/ml. For comparison, a pure chemical, isothiocyanate (AITC, a major antimicrobial compound present in wasabi) was also tested at different concentrations in BHI broth against L. monocytogenes. Each experiment was carried out for 12 h at 37°C with agitation. The viable bacterial concentrations were determined by plate count method using Listeria agar and Salmonella Shigella agar.

Results: The data showed that wasabi at 0.5% to 2% effectively prevented the growth of both L. monocytogenes and Salmonella Typhimurium as evidenced by the lower cell counts compared with the control. At least 5-log unit reduction in cell counts of either bacterium was achieved when the media contained 2% wasabi. In contrast, 2.5- and 7.5-log unit reductions in listerial cell counts were obtained when the media contained 93 ppm and 930 ppm AITC, respectively.

Significance: The results showed that wasabi has high antibacterial activity against L. monocytogenes and Salmonella Typhimurium, suggesting that wasabi has a high potential to be used to effectively control the two pathogens in foods, especially at the point of ingestion of many Ready-to-Eat foods.