Comparison of the inhibitory and lethal effects of synthetic versions of plant metabolites (anethole, carvacrol, eugenol, and thymol) on a food spoilage yeast (Debaromyces hansenii)

The inhibitory and lethal effects of synthetic versions of compounds found in common herbs and spices were compared on a food spoilage yeast Debaromyces hansenii. Separate treatments of sans-anethole, carvacrol, eugenol, and thymol were investigated in potato dextrose broth (PDB) suspension cultures. Inhibitory activity was studied for all compounds at concentrations of 25, 50, 75, and 100 ppm over a 55 h incubation while lethality was investigated for trans-anethole, carvacrol, and thymol at 100 and 125 ppm over a four day incubation. All compounds exhibited at least minor inhibitory activity at a concentration of 25 ppm. During the 55 h incubation period, the minimum concentration for total inhibition by trans-anethole was 75 ppm, while that for carvacrol and thymol was 100 ppm. The maximum level of eugenol examined, 100 ppm, did not completely inhibit outgrowth. Growth curve data were described by the logistic equation which provided for quantitative comparison of inhibition. Lethality was achieved with trans-anethole, carvacrol, and thymol at 100 and 125 ppm as determined by colony forming units (CFU) on potato dextrose agar (PDA) over four days incubation. These findings demonstrate an approach for quantitatively describing inhibition and evaluating the lethal effects of synthetic versions of plant metabolites on D. hansenii. This research may prove useful in future studies identifying active compounds, determining their effective concentrations, and providing strategies for the development of food applications.