## 3 Results and Discussion
### Volatile Compound Profiles in Cheeses
Alcohols were the second most abundant family affected by the cheese category, presenting ten VOCs, enabling us to differentiate PDO Salers and PDO Cantal cheees. Alcohols can generate a wide variety of aromas in cheese, for example, alcoholic, fruity, green, floral, rose, malty, honey, herbaceous, sweet, fragrant, caramel and others. Among the eleven alcohols, nine were more present in PDO Salers cheees compared to PDO Cantal cheees (1-butanol; 3 methyl; 1-butanol, 3-methyl-acetate; 1-propanol, 2-methyl; 1-propanol, 3-methylthio; 2-butanol; 2-heptanol; 2-pentanol; ethanol, propan-2-ol and phenylethanol). Phenol was only present in PDO Cantal cheees and was not detected in PDO Salers cheees. 1-propanol, 3-methylthio was found in our study to only be present in PDO Salers cheees. Phenylethanol was relatively more abundant in Salers cheees compared to Cantal cheees. Its production originates from phenylalanine degradation and is among one of the most odorous aromatic alcohols [4,33]. Ethanol is also detected in higher amounts in Salers cheees in comparison to Cantal cheees, but it has often been detected in different categories of cheees such as Cheddar [32] and Hispanico [34]. This compound is produced from lactose fermentation by starter bacteria [35] and yeasts [36]. Even if it has a limited role in the cheese aroma despite its high levels, it contributes to the formation of esters [37]. It should be noted that the higher presence of 1-butanol,3-methyl in Salers cheese vs. Cantal cheese could not be generalized due to its significant interaction with cow breeds' milk. Ketones were the third family to permit differentiation between the two cheese categories. Three VOCs were more present in PDO Cantal cheees compared to PDO Salers cheees, namely 2,3-pentanedione, 2-hydroxy-3-pentanone and acetoin, with 2,3-pentanedione only being found in PDO Cantal cheees. These findings should be modulated due to the significant interaction of these three compounds with cow breeds' milk. 4-octanone, 5-hydroxy-2-7-dimethyl was only present in PDO Salers cheeses. Generally, ketone or methyl ketones are recognized as key components in the flavor of mold-ripened cheeses such as Blue cheeses [19; 38], but they can be identified in other kinds of cheeses like Cheddar [39], Ricotta [40], Parmigiano Reggiano [41] and Swiss Gruyere [4]. It has been suggested that methyl ketones in non-mold-ripened cheeses may be formed by the enzymatic oxidative decarboxylation of fatty acids by the presence of lactic acid bacteria [42]. Ketones have a typical odor with a low perception threshold [4]. Among these ketone compounds, acetoin is derived from citrate metabolism. Diacetyl can be converted to acetoin and 2.3 butanediol, which is often related to buttery notes. As previously identified by [PERSON] et al. (2015), the content of acetoin varied in Salers cheeses manufactured with the same pasteurized milk, reinoculated with three different microbial communities, hence showing that the flavor production in cheese results from a complex ecosystem and can be varied by inoculating different microbial communities. In another work, it was reported that wild _lactococci_ strains were positive for citrate formation. More particularly, _L. Lactis_ strains used as starter cultures in these cheeses produced acetoin [43]. Concerning volatile acids, five (4-methyl-2-oxoxvaleric acid, 3-methylbutanoic acid, 2-methylpropanoic acid, n-decanoic acid and octanoic acid) were more concentrated in PDO Salers cheeses compared to PDO Cantal cheeses, and 4-methyl-2-oxovaleric acid was only present in PDO Salers cheeses. The presence of volatile acids in Salers and Cantal cheeses may play an important role in aroma production because they have been reported as possible precursors of other aromatic compounds, such as ketones, lactones, aldehydes, esters, methyl ketones and secondary alcohols [44]. Consequently, the PDO samples studied have a high ripening stage (>8 months of ripening) that could explain the high content of secondary aromatic metabolites identified.