# Nanoencapsulation of Essential Oils as Natural Food Antimicrobial Agents: An Overview
## 5 Main Strategies for Nanoencapsulation of Essential Oils  
Nanoencapsulation has promising applications to solve the existing problems of essential oils (EOs), since it has been shown to be an effective means to enhance the stability of EOs against degradation during storage, mask unpleasant taste, and release the antimicrobial at a controlled rate [44; 79]. In this review, data surveys in the literature have found the most applied methods for essential oils and various types of nanocarriers, which are summarized in Figure 2. According to the different encapsulating materials, they are mainly divided into two categories: lipid-based nanoencapsulation systems and polymer-based nanoencapsulation systems. In addition, some nanoencapsulation of antimicrobial agents can be implemented with specially developed equipment, such as electro-spinning, electro-spraying, and nanospraying dryer.  
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\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Encapsulation Method** & **Description** & **Nanoencapsulation** & **Microencapsulation** \\ \hline Emulsification & Emulsification is a process of mixing two immiscible solvents, and the resulting product is referred to as an emulsion. It can be divided into top-down approaches (high-shear stirring, high pressure homogenization, microfluidization, and ultrasonication) and bottom-up (phase inversion temperature, emulsion phase inversion, and spontaneous nanoemulsification) approaches. & & Curcumin encapsulated by Tween 80 and polyglycerol polyicinoleate [59]; lycopene encapsulated in plant (soy and pea) or dairy (whey and sodium caseinate) proteins [60] \\ \hline Spray drying & The basic theory of spray-drying is to feed the liquid into a drying chamber in the form of tiny droplets containing biologically active compounds, supplying hot air to the drying chamber, forming microcapsules in the drying chamber, and recovering them through a cyclone. & Folic acid encapsulated by whey proteins and resistant starch [61]; curcumin encapsulated by maltodextrin matures with or without nature gums [63]; cocoa volatile compounds encapsulated by maltodext and modified starch [64] \\ \hline Freeze drying & The basic principle of freeze-drying is to freeze water contained in a solution or suspension and then evaporate the water molecules from the solution or suspension. & Fish oil encapsulated by poly-e-caprolactone and Pluronic F68 [65] & Blackberry by-product extract encapsulated by maltodext [66]; flaxseed oil encapsulated by alginate, whey protein, and maltodextrin [67] \\ \hline Extrusion & Extrusion technique involves the injection of a bio-based solution into another solution to promote gelation and produce a hard and dense encapsulation system. & Seed oils encapsulated by sodium alginate and high methyl pectin [68] & Canola oil encapsulated by alginate and high methyl pectin [69]; quercetin encapsulated by carnauba wax, shellac, or zein [70] \\ \hline Complex coacervation & Coacervation is a well-known implemented technique to produce micro- and nanosystems. The basic mechanism is the formation of an emulsion by electrostatic attraction between oppositely charged molecules to produce the encapsulating structure. & Folic acid encapsulated by casein nanoparticles [71]; anthocyanins encapsulated by whey protein isolate and beet pectin [72] & Algal oil encapsulated by protein isolate and chitosan [73]; \(\beta\)-carotene encapsulated by casein and gum tragacanth [74] \\ \hline Electro-spinning and electro-spraying & They are two modes of electrohydrodynamic processes that use a charged jet to rotate or spray a polymer solution to produce fibers or particles. & Rose hip seed oil encapsulated by zein prolamine fiber [75]; sandy gum and tween 20 [77]; fish oil encapsulated by a zein prolamine fiber [76] \\ \hline \hline \end{tabular}
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Table 4: Summary of recent studies on micro- and nanoencapsulation of food bioactive compounds.