Essential oils microemulsions prepared with high-frequency ultrasound: physical properties and antimicrobial activity

Abstract

Essential oils (EOs) have demonstrated antimicrobial activity against bacteria due to the effects of their major components. The direct application of EOs may present a rapid volatilization of its components and can decrease their effectiveness. Encapsulation by means of emulsification can provide protection to lipid compounds on a microscale. The aim of this study was to characterize microemulsions of cinnamon essential oil (CEO), oregano essential oil (OEO), and rosemary essential oil (REO) prepared by high-frequency ultrasound and evaluate their antimicrobial activities against Escherichia coli and Listeria monocytogenes. The microemulsions (oil-in-water, O/W) of EOs were prepared using high-frequency ultrasound, applying a wave amplitude of 84 lm for 15 min (REO and CEO) or 30 min (OEO). The antimicrobial activity was determined by inoculating 10 8 CFU/mL of bacteria. Nonsurvival of the bacteria was confirmed by plate count in tryptic soy agar, determining the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The microemulsions exhibited droplet size diameters of 1.98 to 5.46 lm, showing high encapsulation efficiencies (79.91-81.97%) and low separation rates (2.50-6.67%). The MIC and MBC for the microemulsions for both bacteria were 20-75% less than values obtained for the non-encapsulated EOs. This study demonstrates that high-frequency ultrasound is a suitable technique for obtaining stable microemulsions to deliver natural antimicrobials that can be applied to control bacteria of high relevance in food safety.

Effect of Response Surface Methodology-Optimized Ultrasound-Assisted Pretreatment Extraction on the Composition of Essential Oil Released From Tribute citrus Peels

“…UAPE gives rise to instantaneous increases in temperature and energy, promoting the inside of plant cells and thus disrupts these cells via the evaporation of EO through azeotropic distillation. Compared to the conventional HD, UAPE is a simple and cost-effective process that enhances the yield and quality of EO with a significant increase as well as reduces the consumption of time and energy ( 21 , 22 ). The Clevenger apparatus steam distillation is the primary traditional HD for obtaining EO ( 23 ).…”

High-Pressure-Homogenized Clove and Thyme Oil Emulsions: Formulation, Stability, and Antioxidant Capacity

“…Rather, it is more possible in emulsions with the low-viscous components. It has also been reported in some recent studies that the more viscous emulsions tend to be stable for a longer time. , …”

Mexican Oregano (Lippia graveolens Kunth) as Source of Bioactive Compounds: A Review

“…Furthermore, ethanolic extracts of O. vulgare are high in bioactive compounds such as rosmarinic acid, quercetin, apigenin, and carvacrol. Such bioactive compounds are also found in L. graveolens plants, which have been analyzed in terms of the inflammatory response by Propionibacterium acnes , demonstrating an inhibition of 32–37% of inflammation; the authors suggest that the obtained results could be the results of antimicrobial potential and a decrease in the related mRNA (messenger RNA) of interleukins involved in inflammatory processes such as IL-8 and IL-1β [ 99 ]. In another study, an analysis of secondary metabolite extraction, isolation and characterization revealed the bioactivity of the main flavonoids present in oregano extract, the higher inhibition of α-glucosidase (IC 50 value of 37.199 μM) was obtained by Hispidulin.…”