Effects of hydrophilic and lipophilic emulsifier concentrations on the characteristics of Germander essential oil nanoemulsions prepared using the nanoprecipitation technique

The Germanders (Teucrium polium L.) essential oil exhibits antioxidant and bactericidal activities against a wide range of microorganisms; however, its water insolubility, susceptibility to environmental stresses, and intense flavors limit its uses in food formulations. As a solution, in the present study, nanoemulsions of Germanders (Mentha pulegium) essential oil were prepared using a bottom-up nanoprecipitation technique. A central composite design based on the response surface methodology was implemented to investigate the effects of selected lipophilic and hydrophilic emulsifier concentrations. The proposed second-order polynomial models, with relatively high coefficients of determination, could efficiently predict alterations in response parameters due to emulsifier concentrations. The results revealed that both lipophilic and hydrophilic emulsifiers had significantly affected all characteristics of the synthesized essential oil nanoemulsions. Multi-goal optimization analysis suggested that 7.8% and 4.8% concentrations of Span 80 and Tween 80, respectively, could yield the most desirable Germanders essential oil nanoemulsions, with a mean particle size of 78.56 nm, PDI of 0.1722, DPPH radical scavenging of 83.69%, Staphylococcus aureus and Salmonella enterica growth inhibition zones of 10.5 mm and 12.7 mm, respectively. The validity of the models was confirmed by the absence of substantial variations between experimental data and modeling results. While the prepared Germander essential oil nanoemulsions demonstrated acceptable physical properties, they exhibited relatively limited chemical stability during storage at 5°C for 30 days.