Effect of Basil (Ocimum basilicum L.) and Oregano (Origanum majorana L.) Essential Oils on Resistant Escherichia coli in Milk

Abstract

With the increasing resistance of Escherichia coli, a natural alternative to harsh treatments and chemicals is necessary to inhibit or eliminate such bacteria. Therefore, the aim of this study was to study the antibacterial effect of Basil (Ocimum basilicum L.) and Oregano (Origanum majorana L.) essential oils, BEO and OEO, were examined against resistant isolates of E. coli in milk. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of each EO was determined where different concentrations of OEO and BEO were used respectively, (1.5%, 2%, 2.5%, and 3%) and (2.5%, 3%, 3.5%, and 4%). Also, the concentration before the MICs of each EO was combined with heat, treated at 65°C for 30mins to test the effectiveness of the combination on the E. coli isolates. Lastly, the shelf life of the milk was tested with presence and absence of the EOs in room temperature (21-22°C) and refrigerated temperature (4°C) and samples were plated and enumerated for Total Bacterial Count (TBC) for 27 days. The MIC/MBC results were as follows: 2% for OEO and 3% for BEO, respectively. The combination of heat and EOs significantly inhibited the bacterial isolates. Also, the shelf life, where both EOs extended the shelf life of the milk at both storage temperatures. Both EOs showed significant antibacterial effect against the different E. coli isolates, where also upon combining the EOs with heat, the bacteria were completely inhibited. This shows that natural preservation of food using essential oils is an imperative preservation method that can be used in the food industry where further research and studies are necessary to be done on the effect of such EOs on the quality of the food.