# Application of Cinnamon Essential Oil in Active Food Packaging: A Review
## 6 Cinnamon Essential Oil in Food Industry
### Biodegradable Films  
Films produced from natural polymers have fewer desirable properties than synthetic polymers. However, blending biodegradable polymers with additives allows the characteristics of the films to be enhanced, making them competitive and applicable to the market [74]. In this regard, cinnamon EO has emerged as a valuable component in film formulation. When incorporated into the production process, it not only enhances antimicrobial and antioxidant properties, but also confers improved barrier and mechanical properties. Films for food packaging with suitable barrier properties can enhance packaging conditions by protecting food from moisture loss or absorption from the environment [74]. Therefore, the ideal characteristic for films would be high water vapor barrier properties, which would help maintain the quality and extend shelf life of the products [21]. Numerous studies demonstrate that the addition of cinnamon EO can decrease water vapor permeability. For example, [PERSON] and [PERSON] [65] reported a 14.75% decrease in water permeability in GB films when 1.25% cinnamon EO was added. Similar results were found by incorporating cinnamon EO nano emulsions into soybean polysaccharide films [75] and in poly(butylene adipate-\(co\)-terephthalate) (PATB) films loaded with cellulose nanofibers embedded with cinnamon EO [76]. Biodegradable films containing EO usually consist of two parts: a hydrophilic biopolymer region and dispersed hydrophobic EO droplets. The first one is responsible for water vapor diffusion through the films [77], while the EO droplets alter the hydrophilic phase, building tortuous paths through the film and subsequently suppressing the rate of water vapor transmission [78]. In other words, the increased hydrophobic character of the matrix resulting from the addition of cinnamon EO is responsible for reducing water vapor permeability [65; 75; 76]. Another important criterion when choosing film-forming materials is their water solubility [75]. This parameter reflects the water resistance property of the films [79]. In some cases, although the polymer used for film formation has low water solubility, it has adsorption and swelling capabilities [80]. In this regard, it has been observed that the addition of cinnamon EO into the films decreases their solubility in water [65; 75], again due to the increased hydrophobic character of the films resulting from the addition of the essential oil [79]. Cinnamon EO can also modify the optical properties of films. Opacity is an important parameter of films used to wrap food products [21]. Transparent films are suitable for food visibility, while opaque films are suitable as a barrier against light [81]. As a result of the addition of cinnamon EO to the films, an increase in opacity and yellowish of the active films was observed [15; 65], related to the typical yellow color of cinnamon EO [21]. It may not affect other color parameters such as red index (a*) or luminosity (L*) [82]. The mechanical properties of films are an essential quality parameter that determines their quality, feasibility, and applications. A film is considered good when it withstands external stresses, does not easily break, and is plastic, meaning it facilitates stretching and flexibility [21]. Therefore, two factors are involved: tensile strength and elongation at break. The effect of incorporating cinnamon EO into biodegradable films is highly varied, and depending on the polymer used to make the film, it influences these properties in very different ways. For example, [PERSON] et al. [36] reported an increase in tensile strength by increasing cinnamon EO concentration (between 1% and 3%) in the film matrix based on _Eucheuma Cottonii_ seaweed, resulting in enhanced toughness. However, the films exhibited an inverse relationship for elongation at break. Other authors have also elucidated the increase in tensile strength and a decrease in elongation at break of different biodegradable films due to the addition of cinnamon EO [83; 84].