Compositions and methods that utilize a combination of essential oils or other plant-derived extracts or compounds and an emulsifier as an antimicrobial are provided. In some embodiments the compositions further include ozone. In some embodiments, the composition includes one or more plant essential oils, plant extracts, or plant-derived compounds, or combinations thereof, and an emulsifier (such as a saponin). The antimicrobial composition may also include water, peracetic acid, acetic acid, lactic acid, citric acid, and/or hydrogen peroxide. Methods of killing a microorganism, including contacting the microorganism with the disclosed antimicrobial compositions are also provided. The microorganism may be present on a food item or a food contact of non-food contact surface and may be in the form of a biofilm. In some examples, the antimicrobial composition is used one or more times (such as 1 to 5 times).