Optimising Process Parameters for Development of Basil ( Ocimum basilicum ) Oil‐Based Food‐Grade Antibacterial Oil‐in‐Water Microemulsion

Oil‐in‐water microemulsions have budding interest as delivery agents of lipophilic bioactive components in the food industry due to small droplet size and optical transparency. Microemulsion was prepared using basil essential oil, polysorbate 20 and water by stirring at 400 rpm (low energy emulsification method). Microemulsion droplet size decreased when the surfactant concentration was increased. As the concentration of surfactant increased, a decrease in the droplet size was recorded, that is, 73, 36, 25, and 11 nm for BF2, BF3, BF4 and BF5 respectively. However, the trend reversed for optical transparency and viscosity. The droplet diameter of the optimised BF5 formulation was found to be 11 nm with spherical morphology. All the microemulsion formulations were thermodynamically stable, but the BF5 formulation showed marvellous kinetic stability for more than 210 days. The optimised basil oil microemulsion BF5 formulation demonstrated dose and time‐dependent bactericidal efficacy against Bacillus cereus . Ten‐fold diluted BF5 microemulsion caused total loss of viability in 40 and 50 min respectively. Incubation with 100‐fold dilution of BF5 microemulsion showed 20%, 36%, 45% and 61% inactivation of B. cereus in 10, 20, 30 and 40 min correspondingly. Higher dilutions (1000‐fold) of BF5 also demonstrated significant bactericidal activity. Approximately 60% bacterial cell killing was detected in 50 min of exposure to 1000‐fold dilution of BF5 microemulsion. Alteration in bacterial membrane permeability upon microemulsion treatment was suggested by measuring 260 nm absorbing materials leakage. Further this microemulsion can be used as an antibacterial agent for food preservation.