Plant essential oils and components on growth of spoilage yeasts in microbiological media and a model salad dressing

• Plant essential oils and their components were evaluated against spoilage yeasts.
• Of clove, thyme oils and cinnamon oils, the latter was most effective in inhibiting yeast in media.
• Of cinnamic acid, eugenol, carvacrol, thymol, and cinnamaldehyde, the latter was most effective in inhibiting yeast in media.
• Cinnamon oil and cinnamaldehyde, were effective in inhibiting some yeasts in a model salad dressing.
• The compounds show some promise as adjuncts or potential “natural” replacements for sodium benzoate or potassium sorbate.

Essential oils (EOs) and EO components have been widely tested for their antimicrobial properties against microorganisms. However, less is known about the inhibitory properties of essential oil components against microorganisms in foods and, more specifically, spoilage yeasts in a food matrix. Clove bud, cinnamon bark, and thyme oils, and the EO components, trans-cinnamaldehyde, cinnamic acid, eugenol, carvacrol, and thymol first were evaluated for their antimicrobial activity against yeasts in microbiological media. The yeasts tested included Torulaspora delbrueckii, Candida krusei, Schizosaccharomyces pombe, and Zygosaccharomyces bailii. The most efficacious EO components in media were applied to a model mayonnaise-based salad dressing as a food model to determine the effect on spoilage yeast growth. Trans-cinnamaldehyde and cinnamon bark oil were the most effective against yeasts in microbiological media among the compounds tested with minimum inhibitory concentrations (MICs) of 50 mg/L. Thymol and carvacrol had the next most inhibitory activity against yeasts with MICs of 200 mg/L. In a model salad dressing at pH 4.2, trans-cinnamaldehyde at 500 mg/L was most effective among the EO components inhibiting S. pombe and Z. bailii during 4- and 5-day storage, respectively, at 22 °C.