# Nanoencapsulation of Essential Oils as Natural Food Antimicrobial Agents: An Overview
## 6 Effect of Nanoencapsulation on the Antimicrobial Activity of Essential Oils  
As mentioned above, the direct application of essential oils as food antibacterial agents in the food industry faces challenges such as water insolubility, physical and chemical degradation, and effects on the sensory properties of foods. In the past few decades, nanotechnology has gradually become one of the most important technologies in the food industry, especially to improve the anti-corrosion potential of EOs, which may solve these shortcomings in their application [79]. Table 5 reports the latest studies on the efficacy of encapsulated EOs and their bioactive compounds against foodborne pathogens. [PERSON] et al. [130] and [PERSON] et al. [131] reported studies about the antibacterial effects of clove basil, left-handed aroma, oregano, rosemary, and thyme EOs against _Staphylococcus aureus_, _Escherichia coli_, _Pseudomonas aeruginosa_, and _Listeria_. They found the low water solubility and oxidizability of EOs reduce the antibacterial activity of EOs. It has been reported that the EOs are encapsulated by a suitable wall material to prepare nano  
Figure 4: Examples of equipment-based nanoencapsulation: (**A**) electrospinning and (**B**) electrospraying [129]. Reprinted with permission from Ref. [129]. Copyright 2017 Elsevier. sized particles, which can improve the low water solubility of the EOs and improve the stability of its biological activity, thereby improving the antibacterial properties of EOs [132]. [PERSON] et al. [133] found that emulsified citronella oil and clove EOs with nanoemulsification had a stronger antibacterial effect on _Escherichia coli._ [PERSON] et al. [134] studied the effect of surfactant and oil phase composition on the antibacterial activity of eugenol cyanophenol nanoemulsion. It was found that the antibacterial activity could be strengthened after nanoemulsification. In the process of nanoemulsification of eugenol, when adding the ionic surfactant (Tween-80), the antibacterial activity of the nanoemulsion is higher than that of the added non-ionic surfactant (dodecyl sulfate) during the ripening process. Moreover, the lower the amount of soybean oil added to the clove oil, the stronger the bacteriostatic action against _Escherichia coli._ [PERSON] et al. [135] used chitosan to encapsulate sesame oil into nano-sized granules to explore its sustained-release effect and biological activity. As a result, the antioxidant activity of unencapsulated celery oil was stronger than that of chitosan-embedded EOs nanoparticles, but the encapsulated EOs showed stronger antibacterial ability against _Staphylococcus aureus_, _Staphylococcus epidermidis_, _Cactus rod_, _Escherichia coli_, _Salmonella typhimurium_, and _Bacillus subtilis_ than unencapsulated EOs. The same situation was observed when studying the antibacterial activity of d-limonene and oregano EOs after emulsification [136]. Compared with the free EOs, encapsulation can improve the water solubility of EOs, and when the size of EO droplets reaches the nanometer level, this helps to reduce the mass transfer resistance of the nano-scale transport system and enhances the ability of somatic cells to passively adsorb droplets of EOs, thereby reinforcing the antibacterial activity of EOs [137]. [PERSON] et al. [138] found that the emulsified thyme EOs after nano-emulsification had a significant enhancement effect on the bacteriostasis of _E. coli_. [PERSON] et al. [139] prepared EO nanocapsules from _thymus daenensis_ by sonication. They then compared the antibacterial effect of nanocapsules on food spoilage bacteria with that of unencapsulated EO. The results showed that the minimum inhibitory concentration of EOs nanoemulsions was 0.4 mg/mL, and its antibacterial activity was 10 times that of unencapsulated EOs.