Since ancient times, essential oils (EOs) have been used for therapeutic effects and health-promoting benefits, in addition to antiviral, antioxidant, and antibacterial properties. They are complex mixtures of aromatic molecules extracted from plants mainly through distillation. Carotenoids, alkaloids, phenolic acids, flavonoids, monoterpenes, isoflavones, and aldehydes are the main constituents of EOs. [1] EO composition is peculiar for each plant chemotype and varies also within the same genus. [2]
In the last decades, big efforts have been made by food and pharmaceutical industries in order to preserve EO medicinal effects and to increase solubility and bioavailability. These substances are unstable/prone to oxidation, and often it is necessary to mask their unpleasant taste and color. [1]
Nanoencapsulation has gained much attention as a versatile technique to uphold EO original characteristics: by trapping EOs into nanoparticles, it is possible to reduce compound degradation and improve features including controlled release and absorption through the gastrointestinal tract. The inclusion of EO-loaded biopolymeric nanocarriers into food packaging could be a promising innovative method to reduce microbial growth and food oxidation. This is known as active packaging because such packaging interacts with food products to prolong shelf life and improve safety.
The nature of nanocarriers depends on the application, but the encapsulating material must be generally recognized as safe (GRAS). Polysaccharides like chitosan, starches, alginate, cellulose, pectin, and gum can offer valuable assemblies for EO encapsulation. They are particularly suitable for enhancing mucosal adhesion and transport, together with the ability to recognize and bind to specific molecular targets. By modifying the functional groups on the polysaccharidic membrane of the nanocarrier, it is possible to modulate the adhesion of the carrier and the release of the loaded EO.
Proteins also offer a good alternative for biocompatible, biodegradable GRAS building blocks for nano-vehicles: casein, collagen, albumin, and soy proteins are only few examples of molecules capable of behaving as emulsifiers, stabilizers, and thickening agents for the fabrication of nano-structures to enclose EOs. Proteins are highly stable across varying conditions.
Biopolymers as polysaccharides and proteins are often used as wall materials or coating agents because of their high biocompatibility, abundance in nature, and low price. Within different biopolymeric nanocarriers, nanoparticles and nanoemulsions are particularly suitable for EO enclosure: the former are particles with diameter size usually ranging from 1 to 100 nm, and the latter are particulate systems comprising two or more immiscible phases, such as oil, water, and biopolymers (acting as emulsifiers), with diameter size often between 10 and 200 nm. Nanoparticles can be assembled through various techniques such as nano spray drying, electrospraying, self-assembly, or antisolvent precipitation. Nanoemulsions can be formed through high pressure homogenization, ultrasonication, emulsion-phase inversion, etc.
These two kinds of nano-cargos are excellent to encapsulate EOs and to preserve their original features, improving their bioavailability and absorption. Smaller size is associated with greater stability.
Many scientific studies show remarkable increases in antimicrobial, antibacterial, and antioxidant EO power in vitro, making EO-loaded biopolymeric carriers a promising alternative to synthetic conservatives for food and cosmetics. [1]
References
[1] Rehman A, et al. Development of active food packaging via incorporation of biopolymeric nanocarriers containing essential oils. Trends in Food Science & Technology. 2020. doi:10.1016/j.tifs.2020.05.001 [Times cited = 18 (Semantic Scholar)] [Journal impact factor = 11.077]
[2] Fokou JBH, et al. Essential oil’s chemical composition and pharmacological properties. In: Essential Oils – Oils of Nature. Intertech Open; 2020. doi:10.5772/intechopen.86573 [Times cited = 1 (Semantic Scholar)]
Image: Koh KS, Wong VL (eds.) Nanonemulsions: Properties, Fabrications, and Applications. IntechOpen; 2019. doi:10.5772/intechopen.78812
