Antimicrobial properties of microemulsions formulated with essential oils, soybean oil, and Tween 80

Abstract

It was previously found that blending soybean oil with cinnamon bark oil (CBO), eugenol or thyme oil, Tween 80, and equal masses of water and propylene glycol could be used to prepare microemulsions. In the present study, the objective was to determine the antimicrobial activity of the microemulsions in tryptic soy broth (TSB) and 2% reduced fat milk. In TSB, the minimum inhibitory concentration (MIC) of CBO solubilized in microemulsions was up to 625 ppm against cocktails of Listeria monocytogenes, Salmonella enterica or Escherichia coli O157:H7, which was equal to or higher in concentration than free CBO dissolved in ethanol. However, MICs of eugenol or thyme oil in microemulsions were much higher than that of free antimicrobials. Therefore, microemulsions of CBO were chosen to do further study. Inactivation curves of L. monocytogenes or E. coli O157:H7 in TSB or 2% reduced fat milk were tested and fitted using the Weibull model. In TSB, a gradual decrease in cell viability of L. monocytogenes and E. coli O157:H7 was observed with the microemulsion treatments at 625 ppm CBO, which was in contrast to the more rapid and greater inactivation by free CBO. Gradual inactivation of L. monocytogenes in 2% reduced fat milk was also observed in the treatment with 10,000 ppm free or microemulsified CBO. When fitted using the Weibull model, the predicted time to obtain a 3-log decrease of L. monocytogenes and E. coli O157:H7 in TSB or 2% reduced fat milk increased with an increased amount of soybean oil in microemulsions. Additionally, increasing the amount of Tween 80 in mixtures with different mass ratios of Tween 80 and essential oils significantly decreased the log reductions of L. monocytogenes in TSB. Our study showed that microemulsions can be used to dissolve EOs and control the rate of inactivating bacteria, but the composition of microemulsions is to be carefully chosen to minimize the reduction of antimicrobial activities.

Physical, antimicrobial and antibiofilm properties of Zataria multiflora Boiss essential oil nanoemulsion

“…The ZEO makes morphological damage on cell membrane and changes the permeability of membrane (Saei‐Dehkordi et al ., ; Sajed et al ., ). Some studies have investigated antimicrobial effects of EO nanoemulsion prepared by different methods against food pathogenic bacteria (Ma et al ., ; Moghimi et al ., ). They stated that the antimicrobial properties of nanoemulsion are directly attributed with the methods of development.…”

Preservation of traditional Chinese pork balls supplemented with essential oil microemulsion in a phase‐change material package

“…Recently, microemulsification has been proved to be a promising technology to improve aqueous solubilization, physical stability, and the antimicrobial activity of essential oils . Cinnamon essential oil in microemulsion systems has improved water solubility and enhanced antibacterial property against S. aureus . Our previous study also found that CEO microemulsions showed better control efficiency than pure CEO against the postharvest green mold in navel oranges caused by Penicillium digitatum .…”

Efficacy of essential oil formulations against malodor causing bacteria

“…Hammer KA, et al, demonstrated different surfactants affected inhibitory activity of tea tree oil such as, Tween 80 increased MICs of tea tree oil more than Tween 20 14 . In addition, increasing of the concentration of surfactants including Tween 80 in the formulations also decreased antimicrobial activity 13,15 . Therefore, the objectives of this study were to test the antibacterial activity of essential oils and to determine proper surfactants which could maintain antibacterial activity of essential oils.…”

“…Ma Q, et al, reported the decrease of antimicrobial effect of eugenol when mixed with Tween 80 13 . Different surfactants can also exhibit different antimicrobial activity of formulations.…”