# Application of Cinnamon Essential Oil in Active Food Packaging: A Review
## 5 Chemical Composition of Cinnamon Essential Oil
### Antimicrobial Activity  
EOs have been found to be effective as antimicrobial agents against a variety of foodborne pathogens, such as _Escherichia coli_, _Salmonella typhimurium_, _Staphylococcus aureus_, _Listeria monocytogenes_, and _Campylobacter_[39]. In general terms, the antimicrobial capacity of EOs is attributed to the presence of hydrophobic functional groups [40]. This characteristic facilitates the penetration of the compounds present in EOs through cell membranes, resulting in inhibitory activity. It is important to note that the antimicrobial activity of EOs is more prominent against Gram-positive bacteria than against Gram-negative bacteria due to differences in the composition of their cell walls. Gram-positive bacteria, with a cell wall composed mainly of peptidoglycan, offer less resistance to the penetration of the hydrophobic molecules present in EOs. In contrast, in Gram-negative bacteria, the peptidoglycan layer is thinner and surrounded by a double phospholipid layer, which hinders the penetration of hydrophobic compounds and makes them more resistant to EOs [40]. Cinnamon EO is known for its high antimicrobial activity, even at low concentrations. This activity is attributed to its high cinnaldehyde content, since the antimicrobial efficacy of both cinnamon EO and cinnaldehyde are almost equivalent. However, it should be noted that this activity is also influenced by minor components and the target microorganism [41]. The mechanism of action of cinnamaldehyde is not fully determined, although it is suggested that at low concentrations it may inhibit cell division. At higher but sublethal levels, it is thought to function as an ATPase inhibitor, while at lethal concentrations, it causes cell membrane changes resulting in bacteria death [42]. Cinnamaldehyde is also known to be able to inhibit the formation of membrane porins, thus reducing their resistance to osmotic stress and leading to the reduction of biofilm formation [2]. This EO is highly active against various foodborne microorganisms such as _E. coli_, _Pseudomonas aeruginosa_, _S. typhimuriumium_, _Bacillus subtilis_, _Bacillus cereus_, _S. aureus_, _L. monocytogenes_, _Microococcus luteus_, _Klebsiella_ spp., _Candida albicans_, and _Aspergillus niger_[43; 44; 45]. [PERSON] et al. [46] evaluated the antimicrobial activity of several EOs including oregano, clove, black pepper, cinnamon, and thymme. Their results showed that cinnamon exhibited minimum inhibitory concentrations (MICs) of between 0.052 and 0.178 mg/mL and minimum bactericidal concentrations (MBCs) of between 0.058 and 1.084 mg/mL against different microorganisms such as _Salmonella_ spp., _L. monocytogenes_, _S. aureus_, _E. coli_, and _S. typhimurium_. These concentrations were significantly lower than those observed for the other EO. Clove, another important EO with antimicrobial properties, showed MIC values between 0.037 and 1.995 mg/mL, and oregano showed values between 0.718 and 4.784 mg/mL, with these concentrations being much higher than those of cinnamon EO, thus demonstrating the excellent antimicrobial activity of cinnamon EO. However, MICs even lower than the above (between 0.1 and 0.4 mL) have been found for certain microorganisms such as _B. subtilis_, _B. cereus_, _S. aureus_, _E. coli_, and _S. typhimurium_[47]. Moreover, EOs also exert antifungal effects by disrupting the fungal cell wall and cell membranes, coagulating the cytoplasm and ultimately damaging cellular organelles and leading to the leakage of cell contents [17]. [PERSON] et al. [48] proposed that fungal cell membrane lysis is caused by interactions and binding of EOs to ergosterol (main sterol present in fungal cell membranes that controls permeability and fluidity).