Application of the mixture design for optimum antimicrobial activity: Combined treatment of Syzygium aromaticum, Cinnamomum zeylanicum, Myrtus communis, and Lavandula stoechas essential oils against Escherichia coli

This study investigates the optimal combination of clove, cinnamon, lavender, and myrtle essential oils (EOs) against Escherichia coli. After the GC/MS analyses, the antimicrobial activities of the four EOs were screened. Afterward, a statistical mixture design established the right EOs' combination capable of protecting milk from E. coli. Results illustrated that the EOs were chemically different and efficient against 14 bacteria. Hence, the simplex-centroid mixture design was used to build polynomial models describing the relationship between the anti-E. coli effect and the proportion of each EO. Result depicted that the lowest bacterial survivability was equal to 1.5 x 10(6)center dot CFU center dot ml(-1) for the combination of cinnamon and lavender; and the combination of cinnamon, lavender, and clove at a concentration of 2 mg/ml. The application of the statistical design concluded that the optimal combination corresponds to 2.4% S. aromaticum, 38.2% L. stoechas, and 59.4% C. zeylanicum. The combination validation exhibited its efficiency as it restricted the E. coli viability to 1 x 10(6)center dot CFU center dot ml(-1). Practical applications EOs are the new eco-friendly preservative for food. Their combination (using the right sources and proportions) allows better protection against germs. In this study, the obtained formula may be of interest in the milk and dairy industry as it contributes to protecting milk (and dairy products) against E. coli contamination.