## 3 Results and Discussion
### Relationship between Volatile Compounds and the Odor Sensory Profile  
A total of 120 volatile compounds were extracted by SPME and identified (Table S2). The groups of compounds were twenty-three aldehydes, twenty alcohols, sixteen terpenes, thirteen esters, twelve ketones, eleven alkanes, ten aromatic compounds, eight acids, and seven sulfur compounds. The MFA, including volatile and sensory data, explained 65.02% of the variability of the data, and this analysis was applied in order to explore the change of different groups  
Figure 1: Biplot of Generalized Procrustes Analysis for the six days of ripening of chorizo samples (D0, D5, D12, D19, D26, and D33), and each session (S1 and S2), and the loadings of sensory descriptors. of volatile compounds during chorizo ripening, Figure 2. The first MFA dimension (F1) explained 39.30% of the variability, allowing the first days of ripening, D0 and D5, to be differentiated; these were located on the positive side of F1, with the remaining days of ripening, D12, D19, D26, and D33, on the negative side of F1. Terpenes were the principal groups of volatile compounds related to the pepper, greasy, and pork meat odors at days D0 and D5, Figure 2B. The terpenes were the compounds occurring at the highest amounts at this time of the process, including \(\alpha\)-thujene (T1), \(\alpha\)-caryophyllene (T16), \(\alpha\)-terpinene (T4), thujene (T7), 3-carene (T11), and \(\beta\)-caryophyllene (T15), Table S2. The main sources of these compounds were spices, pepper, and paprika [11; 48], which probably explains their relationship with the pepper odor. In general, the major terpenes decreased during ripening (Table S2). [PERSON], [PERSON] et al. [15] found similar results and suggested that the volatile compounds from spices, such as pepper and garlic, were lost and/or degraded during ripening. Nevertheless, only T11 and T15 were significant (\(p<0.05\)), probably because the amount of spice was not the same in each sample of chorizo analyzed, which generated a large data variation, as is common in flavor analysis in meat products [31]. Sulfur compounds such as allyl mercaptan (S1) and allyl sulfide (S4) showed a slight increase (not significant \(p>0.5\)), Table S2, but allyl methyl sulfide (S2) and dimethyl disulfide (S3) decreased significantly (\(p>0.05\)). In general, sulfur compounds decreased during ripening, and [PERSON] et al. [52] reported a similar finding for this group of compounds. Some sulfur compounds came from the meat, and these were formed from the degradation of amino acids with sulfur content, such as methionine, cysteine, and cysteine, via Strecker degradation to thiols [53], as well terpenes, like styrene, which came from the meat as a consequence of their presence in animal feedstuff [11], so the relationship between sulfur and terpene compounds with pork meat odor was expected. Figure 2: **(A)** Map of days of ripening, D0, D5, D12, D19, D26, and D33. **(B)** Evolution of the groups of volatile compounds and eight odors in chorizo samples using a Multifactor Analysis (MFA). Another group of compounds detected at days D0 and D5 were alkanes, such as pentane (A1), hexane (A2), and isobutene (A3), and some alcohols, such as octan-1-ol (L19), butan-1-ol (L5), and hexan-1-ol (L12). Many of these were derived from fatty acids; the source of the fat was the back fat used to make the chorizo, and this possibly explains their relationship with the greasy odor. Alcohols, aldehydes, and acids were the main groups of volatile compounds present in the middle of the ripening time, D12 and D19, and were related to vinegar, fermented, and chili odors. These were located on the negative side of the second MFA dimension (F2) that explained 25.73% of the variability; Figure 2. During these days, ethanol (L1) was the major alcohol (significant at \(p<0.05\)), Table S2; this came from the catabolism of amino acids and carbohydrate fermentation, and was close to the fermented odor, meaning a strong relationship with alcohol existed. [PERSON] et al.