Chemical composition and antibacterial activity of Eugenia brejoensis essential oil nanoemulsions against Pseudomonas fluorescens

The objectives of this work were to produce nanoemulsions containing 1% (v/v) of Eugenia brejoensis Mazine essential oil (EO) at different rotation speeds (8000 and 12,000 rpm) and evaluate the antimicrobial effects of this EO against Pseudomonas fluorescens (ATCC 13525). Droplet average droplet size, size distribution, surface charge, and functional groups were taken into account. Droplet size was observed to decrease at higher rotation speeds (from 355.63 ± 21.70 to 143.13 ± 1.1 nm). Aggregation and sedimentation processes were prevented by a food-grade emulsifier, mainly in the system obtained at 8000 rpm. This stabilizing effect was confirmed by suitable ζ potential values (ca. −30 mV). Both nanoemulsions presented in vitro inhibitory effect against P. fluorescens. Nonetheless, the nanoemulsion containing ca. 355-nm-dia droplets presented larger inhibition zones. Hence, this nanoemulsion was tested in sliced ham preservation, but decreased inhibitory effects compared to in vitro tests were observed because insufficient oil content was incorporated into the slices. Therefore, while these nanoemulsions presented in vitro antimicrobial effectiveness, their application in real food products may be feasible upon the optimization of their synthesis conditions.