A study of antimicrobial effect of Thymol, Carvacrol, Eugenol and Menthol on food spoilage bacteria in agricultural crops and dairy products

Currently, consumers are aware of the side-effects of chemical additives and are more interested in natural antibacterial compounds as food preservatives, like herbal essential oils and extracts. In this study, the antimicrobial effect of some main components of the essential oils, including thymol, carvacrol, menthol and eugenol has been evaluated against Bacillus cereus</em> (PTCC 1154), Pseudomonas nigrifacience </em>(ATCC 19375), Erwinia carotorova</em> (PTCC 1675) and Xanthomonas campestris </em>(PTCC 1473) by broth microdilution method and agar disc diffusion method. According to the results, the lowest MIC was reported for Thymol which was 50 ppm (Pseudomonas nigrifacience</em>, Erwinia carotorova</em> and Bacillus cereus</em>) and the maximum MIC for Pseudomonas nigrifacience </em>was 100 ppm due to menthol and 125, 125 and 108 ppm for Bacillus cereus, Erwinia carotorova</em> and Xanthomonas campestris</em> respectively due to Eugenol. Menthol presented the broadest growth inhibitory zone (8.9 mm) for Pseudomonas nigrifacience</em> and the narrowest inhibitory zone was reported for Eugenol against Erwinia carotorova</em> (5.9 mm). Menthol and eugenol were the strongest and weakest antimicrobial agents respectively (p-value<0.05). However, all tested components inhibited the microorganisms at different levels and are potent to be used as food preservatives.