Minimum Inhibitory Concentration (MIC) of Essential Oils Against Microorganisms: Methods, Function, Accuracy Factors and Application

Essential oils (EOs) from plants have attracted the attention of scientists due to their multiple biological activities. Antimicrobial activity of essential oils is the main reason for their widespread use in industries, which is determined through minimum inhibitory concentration (MIC) by using in vitro models. Therefore, the MIC is a crucial parameter to evaluate the antimicrobial potential of EOs. 492 papers were screened through the critical review of the related literatures in the past 50 years using four databases and read deeply for an outline. This review first listed common MIC determination methods of EOs, including agar diffusion method, agar dilution method, broth dilution method, E-Test, thin-layer chromatography-bioautography, etc. and their merits and demerits were introduced in detail. Agar and broth dilution methods are the gold standards in a more exact approach for MIC determination. Then, their functions and factors influencing the accuracy were listed and analyzed deeply. The application of the MIC determination in food and pharmaceuticals was finally discussed. This study is believed to help researchers to choose the right method and conditions for research and development of the tested EOs.