# Nanoencapsulation of Essential Oils as Natural Food Antimicrobial Agents: An Overview
## 5 Main Strategies for Nanoencapsulation of Essential Oils
### Biopolymer-Based Nanoencapsulation
#### 5.1.1 Polysaccharide-Based Biopolymers  
Polysaccharide-based biopolymers can be classified as homopolysaccharides or heteropolysaccharides depending on the number and types of monosaccharide units constituting the chain. Because of the different chemical properties of the monosaccharide units, the polysaccharides also have different degrees of polymerization (unit monosaccharide number), molecular weight, hydrophobicity/hydrophilicity, electrostatic charge, gelation properties, and viscosity, which are different from each other. Polysaccharides used for encapsulation usually have the following advantages: low toxicity and low cost, high stability in a wide pH range, and good biodegradability [81].  
Cyclodext (CDs) are cyclic oligosaccharides with a truncated cone shape and are derived from starch, which is a traditional wall material used to prepare nanocapsules [83]. In this process, the inner side of \(\beta\)-cyclodextrinrin is an inner wall of a cavity formed by a combination of a hydrophobic epoxy group and a C-H bond, and the outer side of the  
Figure 2: Schematic representation of the different nanoencapsulation systems for EOs.  
ring is a primary alcoholic hydroxyl group on C6, which exhibits a hydrophobic inner side and a special structure of the outer hydrophilic structure. The molecular structure can form an inclusion complex with many guest molecules, and the core material is coated in the cavity, which can slow down the reaction with the control of light and oxygen. Meanwhile, \(\beta\)-cyclodextrinrin can mask the pungent odor of some oils, compared with other wall materials. [PERSON] et al. [84] used \(\beta\)-cyclodextrinrin as a cryoprotectant to prepare eugenol nanocapsules by the emulsion diffusion method. The morphology and structure of the nanocapsules were analyzed by scanning electron microscopy. The results showed that \(\beta\)-cyclodextrinrin can be used as a cryoprotectant to maintain the physical stability of eugenol and protect eugenol from freezing damage [85].  
Chitosan (CS) is a cationic polysaccharide found in nature, which is obtained by deacetylation of chitin. CS is suitable for the preparation of nanocarrier systems because of its biodegradability, pH sensitivity, and easy chemical modification [86]. Although chitosan nanoparticles can be prepared by different methods, ionic gelation is the most widely used method. The method is simple and mild, and the activity of the encapsulated substances can be maximized. [PERSON], [PERSON] et al. [87] prepared chitosan nanoparticles (125-175 nm) by this method, and their results showed that encapsulated EOs improved stability and enhanced antifungal activity against _Botrytis cinerea_. In another study, ionic gelation, applied to prepare O/W emulsion, was carried out to obtain chitosan nanoparticles enclosing thyme essential oil [88].  
Starch is an interesting renewable polysaccharide and one of the main sources of glucose in the human body. Moreover, the modifications of its physical, chemical, or biochemical characteristics can impart a variety of unique properties to this biopolymer. Therefore, starch and/or its derivatives are often used for the encapsulation of active substances such as carotenoids and essential oils [89]. [PERSON] et al. [90] obtained starch nanoparticles (300-400 nm) by dissolving sago starch in NaOH/urea, adding the obtained starch solution dropwise to absolute ethanol under magnetic stirring, and centrifuging the obtained suspension.