## 3 Results and Discussion
### Relationship between Volatile Compounds and the Odor Sensory Profile
[52] found that alcohol also contributes to beef flavor. Other alcohols, such as 2-methylbutan-1-ol (L8) and 2-phenylethylanol (L20), were derived from amino acid degradation; these were products of Strecker reactions, associated with the Maillard reaction [20] or caused by bacterial enzymes [16]. Additionally, phenol (L18) occurred in the highest amount at D12 and D19 (\(p<0.05\)), then decreased at the end of ripening, probably due to alcohol's participation in ester formation. Acetic acid (C1) was also related to the fermented and vinegar odors. C1 was the most abundant acid during the process and came from carbohydrate fermentation, paprika, or compounds from Maillard reactions [11]. It occurred in the highest amount at D19 (\(p<0.05\)), then had a slight decrease. Similar results were obtained previously [16; 17; 18]. Other important acids in these days were propanoic (C2), pentanoic (C4), and heptanoic acids (C6). The linear saturated aldehydes propanal (AD1), butanal (AD3), and heptanal (AD9) increased significantly (\(p<0.05\)) at days D12 and D19, then decreased by the end, D33, and were related to the vinegar and chili odors, Figure 2B. In addition, 2-methylpropanal (AD2) also increased on these days, but not significantly. The branched aldehyde AD2 originated from valine degradation [54]; AD1, AD3, and AD9 were probably formed by an oxidation reaction of their respective alcohols, while AD9 could also have come from autoxidation of fatty acids [53]. The last days of ripening, D26, located on the negative side of F1, and D33, on the positive side of F2, Figure 2A, were related mainly to the rancid odor and various groups of volatile compounds generated by the increase of degradation of amino acids, and oxidation of fatty acids by bacterial enzymes, which related to an increase of molds and LAB at days D26 and D33 [36; 51]. The compounds derived from proteolysis or degradation of amino acids, such as 3-methlbutan-1-ol (L7), 2-methylbutan-1-ol (L8), ethyl-3-methyl-butanoate (E6), and benzaldehyde (AD12), showed significant differences (\(p<0.05\)), except for the last one; similar findings for these aldehydes were reported previously [20; 53]. At D33 of ripening, hexanal (AD7) was the major aldehyde (significant \(p<0.05\)); this came from the oxidation of n-6 fatty acids and linoleic and arachidonic acids [52], so has been used as a marker of both lipid oxidation and flavor deterioration [15]. Therefore, the relationship with the rancid odor was expected. The unbranched alcohols, pentan-1-ol (L9), hexan-1-ol (L12), and octan-1-en-3-ol (L15), increased significantly (\(p<0.05\)) at the end of ripening; these came from lipid autoxidation reactions or incomplete \(\beta\)-oxidation [18; 19]. Due to their origin, [PERSON] et al. [55] proposed L12 and other volatile compounds be used as a shelf-life marker in raw beef. The ketones, pentan-2-one (K3), pentane-2,3-dione (K4), and heptan-2-one (K6), occurred in the highest amounts (significant \(p<0.05\)) at D33. These can be produced by lipid oxidation, oxidation of free fatty acids, alkane degradation, or bacterial dehydrogenation of secondary alcohols [53]. Esters were the least abundant group but had an important impact on chorizo odor, probably due to their low threshold, and commonly generate fruit notes [16]. However, in this study, esters were related to the rancid and fermented odors. Esters were formed through the esterification of alcohols and carboxylic acids following microbial esterase activity, mainly attributed to staphylococci, LAB, yeast, and molds [56]. Ethyl butanoate (E3), ethyl pentanoate (E8), methyl octanoate (E10), ethyl octanoate (E11), and ethyl decanoate (E12) significantly (\(p<0.05\)) increased their concentrations during ripening, Table S2. The most abundant was ethyl (2E,AE)-hexa-2,4-dienoate, which came from the mixture of sorbic acid and natamycin applied to the sausage casing to prevent surface molds, as previously reported [17].