Introduction: The essential oil of lemon balm (Melissa officinalis) and pennyroyal extract (Mentha pulegium) are widely used for food flavoring and beverages due to the pleasant spicy flavour. The antibacterial activities of these plants have been proven in several studies. The aim of this study was to investigate the growth inhibition of food spoilage yeasts by lemon balm essential oil and extract of pennyroyal. Materials and Methods: The chemical compounds of the essential oils were analysed and identified by GC apparatus connected to the mass spectrometer detector. The total phenolic compounds of the extract of pennyroyal were determined by Folin-Ciocalteu method. The anti yeast activities of (minimum inhibitory concentration and mortality) lemon balm essential oil and extract of pennyroyal against yeasts causing food spoilage were assessed by using microdilution. Results: The results showed that geranyl acetate (25.29%), sytral )12.38%(, z-sytral )14.3%(, e- sytral (9.45%) and geraniol (9.55%) were the main constituents of the essential oil of lemon balm. The total amount of phenolic compounds in pennyroyal extract based on gallic acid was 252.48±0.2 mg/gr. Minimum inhibitory concentrations of lemon balm essential oil against Saccharomyces cerevisiae, Rhodotorula glutinis and Kluyveromyces marxianus were 1.562, 3.125 and 0.195 µL/mL, respectively and the minimum inhibitory concentrations of pennyroyal extract, for the above mentioned microorganisms were 17.500, 14.583 and 14.583 mg/mL, respectively. Conclusion: The lemon balm essential oil and the extract of pennyroyal have shown antimicrobial activities and might be employed as natural products in food industry successfully.
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