Ultrasonication-assisted formation and characterization of geraniol and carvacrol-loaded emulsions for enhanced antimicrobial activity against food-borne pathogens
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Gum arabic stabilised oil-in-water emulsions were prepared through ultrasonication approach for the incorporation of natural, plant-based antimicrobial compounds, geraniol and carvacrol. The oil phase of formulated emulsions was constituted with geraniol and carvacrol, incorporated at various ratios of 1:0, 2:1, 1:1, 1:2, and 0:1 (v/v). The ultrasonication procedure was followed using a frequency of 20 kHz at 40% amplitude for 5 min. These emulsion systems were characterized for mean particle diameter, polydispersity index, ζ-potential, storage stability and creaming index. In addition, emulsion microstructure was studied using confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). Evaluation of antimicrobial activity of the functional emulsions was carried out against Gram-positive bacteria Bacillus cereus MTCC 430 and Gram-negative bacteria Escherichia coli MTCC 443. The results demonstrated that geraniol: carvacrol (1:1) emulsion formulation displayed good stability with particle size (202.7 ± 4.17 nm), polydispersity (0.282 ± 0.001), ζ-potential (− 19.37 ± 0.06 mV) and no visible separation of cream was observed. Furthermore, the CLSM and TEM observations confirmed the presence of stable emulsion. In addition, the antimicrobial susceptibility tests demonstrated collaborative activity and prolonged antibacterial efficacy for the combined essential oil-based emulsion against both the model bacterial pathogens.
KeywordsEssential oil emulsion Geraniol Carvacrol Food-borne pathogens Antimicrobials
The authors would like to thank the Science and Engineering Research Board, Govt. of India, for providing financial support for conducting research work through a research grant to Dr. Preetam Sarkar (YSS/2015/000546). The authors would also like to acknowledge technical support extended by Sukanta, Susanta Pradhan, and Subhabrata Chakraborty, National Institute of Technology, Rourkela, for assistance with Zetasizer Nano ZS, confocal laser scanning microscopy imaging and TEM imaging, respectively.
Compliance with ethical standards
Conflict of interest
The authors report no conflict of interest.
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