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

• Published in: Journal of food science and technology Vol. 57; no. 11; pp. 4133 - 4142
• Main Authors: Dávila-Rodríguez, M., López-Malo, A., Palou, E., Ramírez-Corona, N., Jiménez-Munguía, M. T.
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.11.2020; Springer Nature B.V
• Subjects: Antiinfectives and antibacterials; Antimicrobial activity; Antimicrobial agents; Bacteria; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Cinnamon; E coli; Emulsification; Encapsulation; Escherichia coli; Essential oils; Exercise; Food safety; Food Science; Lipids; Listeria; Listeria monocytogenes; Microemulsions; Minimum inhibitory concentration; Nutrition; Oils & fats; Oregano; Original; Original Article; Physical properties; Ultrasonic imaging; Ultrasonic testing; Ultrasound; Volatilization; Encapsulation; Antimicrobial activity; Microemulsions; Essential oils; High-frequency ultrasound
• ISSN: 0022-1155; 0975-8402
• DOI: 10.1007/s13197-020-04449-8

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 µm 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 µm, 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.