Antibacterial effects of peppermint, \u3ci\u3eMentha piperita\u3c/i\u3e essential oil in free-form and in nanoparticles on \u3ci\u3ePseudomonas fluorescens\u3c/i\u3e

Mentha piperita, commonly known as peppermint originally came from Europe and the Middle East and its oil is commonly used in traditional medicine and aromatherapy. Like many other free essential oils (EO), peppermint oil is believed to possess antimicrobial properties. However, the application of EO in food as an antimicrobial agent has yet to be established. This would require proper formulation of the EO for it to be viable in foods. This study aims to test the effects of both free Mentha piperita EO and Mentha piperita EO nanoparticles against Pseudomonas fluorescens and compare their inhibitory effects. We used nanoparticles of encapsulated Mentha piperita EO in a shell of fully hydrogenated soybean oil (FHSO) and expect that the inhibitory effects of these nanoparticles would be greater than that of the free EO due to the ability of the shell to protect the EO and control its dispersion. We observed for the presence of antibacterial properties using various methods such as well diffusion, disc diffusion, optical density measurements and plate counting of serial dilutions. We found that the best method that produced quantifiable results was to perform serial dilutions and plate count them after incubation. In these series of experiments, we demonstrated that free Mentha piperita EO inhibits P. fluorescens growth but have yet to demonstrate a similar effect with the EO nanoparticles