## 5 Edible Films and Coatings Containing CEO
### Lipid Oxidation in Edible Films and Coatings Containing CEO  
When lipids interact with oxygen molecules, deterioration reactions known as oxidative rancidity are generated. These transformations reduce the nutritional value of the food and give rise to unpleasant odours and flavours [87]. Regarding PV, the information extracted indicates that the use of coatings decreased lipid oxidation. [PERSON] et al. [36] mentioned that the acceptable limit for hydroperoxide formation is 5 mEq O\({}_{2}\)/kg lipid. [PERSON] et al. [56] found that the peroxide value in pork belly treated with films containing 0.75% (_w/v_) of CEO at the end of the investigation time (15 days) was lower when compared to control samples. [PERSON] et al. [21], who studied the effect of CEO incorporated in basil seed gum on camel meat, assumed that the reduction in PV is due to the phenolic components of the EO since the presence of these molecules can delay the formation of peroxides, therefore decreasing lipid auto-oxidation in meat. [PERSON] et al. [50] explained that the decomposition of unsaturated fatty acids leads to the formation of peroxides. These molecules indirectly influence the sensory characteristics of meat (flavour changes) as well as the loss of nutrients. The observation of PV reduction (control: 5.02, 1% CEO: 3.24 and 1.5% CEO: 2.64 mEq of O\({}_{2}\)/kg fat) could be associated with the CEO antioxidant activity because phenolic compounds act as potent scavengers of free radicals by donating a hydrogen atom from their OH group [50]. Similarly, [PERSON] et al. [15] reported that the resulting phenolic radicals are stable molecules that do not establish or increase oxidation because they present resonant structures thanks to the phenolic ring. When peroxide decomposes, secondary oxidation occurs and aldehydes and ketones are formed. The main aldehyde produced by this reaction is MDA [42]. [PERSON] et al. [21] and [PERSON] et al. [65] mentioned that these molecules generate unpleasant odours in meat. Therefore, the TBARS index is used to quantify the secondary products generated by auto-oxidation, thus providing information on the progress of the product oxidation. [PERSON] et al. [50] evaluated the effectiveness of a film containing CEO as an antioxidant in samples of Wuchang bream (_Megalobrama ambyczphala_), where a decrease in the amount of MDA was evident in the treated samples compared to the control samples (control: 3.01, 1% CEO: 1.70 and 1.5% CEO: 1.26 mg MDA/kg of tissues). The authors assumed that this reduction is due to the bioactive molecules present in the EO, given their antioxidant potential, which allowed the elimination of free radicals present in their samples, thus hindering lipid oxidation. However, [PERSON] et al. [44] stated that phenolic compounds do not absorb oxygen but rather prevent the formation of free radicals, thus neutralising fatty acids. Likewise, some authors, including [PERSON] et al. [68], suggested that the limitation of the formation of secondary compounds is due to the barrier effect of films and coatings, which prevents direct contact between oxygen and meat. [PERSON] et al. [88], studying _Sardine pilchardus_ and _Boops hoops_, suggest that to guarantee the quality of fish, the maximum acceptable level is 5 to 8 mg MDA/kg. However, [PERSON], et al. [68] argued that in fish meat with a MDA content greater than 2 mg/kg, there are already certain undesirable odours, but it does not affect the quality of the product. A number of authors agree that the main compounds of CEO can inhibit the oxidation reactions in a food item. [PERSON] et al. [49] studied the release of eugenol and its influence on oxidative reactivity. The study concluded that eugenol is responsible for the inhibition of lipid oxidation. On the other hand, [PERSON] et al. [61] analysed the relationship between the concentration of CEO in coatings and storage time with respect to the decrease in MDA content present in meat.