## 4 Discussion
For instance, a similar effect was observed when using CH coatings with roscamy or oregano EOs on beef steaks [45], chicken breasts [42], and chicken burgers [46], or active films based on CH and roscamy EO on fresh poultry meat [47], as well as CH with a Brazilian EO richin 1,8-cineole on ground beef [48]. Even a mixture of CH and a mint extract incorporated into the recipe of commercially produced pork cocktail salami made them more resistant to lipid oxidation throughout the storage period [49]. The acids, alcohols, aldehydes, esters, hydrocarbons, and ketones that make up the VOCs released by the untreated beef samples have all been described before by other authors working on meat characterisation through SPME-GC/MS or other techniques [50]. As odorant molecules, hexanoic acid, 1-pentanol, and 3-hydroxy-2-butanone are described as fatty, pentanoic acid as meaty, 2,4-bis(1-methylethyl)-phenol as woody, pentanol as peanut, 2-butanone as green, ethanol and 1,3-dimethylbenzene as sweet, and ethyl acetate and 3-methyl-1-pentanol as fruity [51; 52; 53; 54]. Surprisingly, treatment with the CH solution only slightly altered the volatile emissions, suggesting a mild effect on the patties' smell. The presence of specific plant secondary metabolites among the VOCs deriving from the EO-containing beef samples was consistent with the chemical compositions of the EOs themselves. As mentioned earlier, 1,8-cineole (28.1%) was the main compound found in the _L. nobilis_ EO, with smaller amounts of linalool (5.5%) and \(\gamma\)-terpinene (0.6%) also detected. Different isomers of other constituents were also present, such as m-cymene (0.5% of p-cymene in the EO), \(\beta\)-phellandrene (0.2% of \(\alpha\)-phellandrene), and \(\delta\)-2-carene (0.1% of \(\delta\)-3-carene). Eugenyl acetate was likely derived from eugenol (3.4% in the EO) via acetylation and p-menthene from the rearrangement of terpen or cyclic compounds. The same phenomenon could explain the presence of p-menthene among the VOCs emitted by the beef treated with the _P. nigrum_ EO-enriched CH solution. Even in this case, compounds corresponding to the original EO composition (i.e., linalool = 0.3% in the EO) or their isomers (e.g., \(\delta\)-2-carene from \(\delta\)-3-carene = 4.7%, \(\beta\)-phellandrene from \(\alpha\)-phellandrene = 0.6%, \(\gamma\)-terpinene from \(\delta\)-terpinene = 0.3%, m-cymene from p-cymene = 0.2%) were identified. As odorant molecules, 1,8-cineole is described as fresh and eucalyptus-like, \(\delta\)-2-carene as sweet, linalool as floral and citrusy, p-menthene as minty, \(\beta\)-phellandrene as peppery-minty, and \(\gamma\)-terpinene as green and citrusy [55]. In all the beef patties treated with the EO-containing formulations, a decrease in the prevalence of these secondary metabolites was observed over time. This lack of persistence can be attributed to their volatility, which is related to their low molecular weight and is one of the main limitations to the use of EOs and their individual components in applications that require long-term release of the active ingredient [56]. Ethanol was detected in all beef patties and has been negatively correlated with changes in sensory properties [57] and spoilage [58] in previous studies. Indeed, its trend during the storage period followed the same pattern as TBARS. The quantity of ethanol identified through SPME-GC/MS analysis in all the samples at T0 was comparable. It then increased at T1 and T2, with only the _L. nobilis_ EO-enriched CH solution being able to maintain the ethanol level statistically lower than those of the other treatments and control. Both the EO-containing samples also showed higher levels of hexanoic acid and 1-pentanol (associated with fatty odours), the _P. nigrum_ EO increased 2-butanone (green odour) and 1,3-dimethylbenzene (sweet odour), and the _L. nobilis_ EO intensified the release of 2,4-bis(1-methylethyl)-phenol (woody odour) [55]. Regarding the protection against _C.