## 3 Results and Discussion
### Variation of Volatile Metabolites Profiles During Sotol Must Fermentation  
The transformation of the volatile profiles during the fermentation of sotol must is an important feature that shapes the organoleptic attributes of the final distilled spirit. The chromatograms of the volatile metabolites detected in fermented sotol (_Dasylirion_ sp.) must are shown in Figure S4. Their retention times and identification are exhibited in Table 1, and the classifications of the metabolites by chemical groups are shown in Figure 3. A total of 57 compounds were identified and grouped into ten classes based on the chemical properties as follows: alcohols (9), aldehydes (6), acids (7), ethers (3), esters (14), hydrocarbons (3), amines (6), alkenes (2), acetals (2), and others (5). Until today, there have been no reports about volatiles profiles in fermented sotol must. [PERSON] et al. (2010) reports a significant effect on the organoleptic characteristics of the distillate sotol given by alcohols, volatile acids, aldehydes, esters, and polyphenols. [PERSON] et al. (2006) performed a gas chromatography (GC) and ion chromatography (IC) analysis to study Mexican spirits such as sotol, where the identification of alcohols, aldehydes, and esters was reported, and the anionic profile of sotol exhibited a high content of nitrate. Of the ten chemical groups used to classify the volatile metabolites produced during fermentation (Figure 3), alcohols was the most predominant category; secondly, the group of ethers, followed by esters, then amines, and minimum levels of acids and aldehydes were observed. These volatile metabolites derive from the alcoholic fermentation by yeasts and other microorganisms present in sotol must, which metabolize carbohydrates, fatty acids, amino acids, and other organic components. Thus, likewise, there is the primary production of ethanol by yeasts of other volatile metabolites, such as aldehydes, ketones, organic acids, and higher alcohols [52]. Yeasts can produce esters by the reaction of fatty acids when ethanol is produced in excess [53]. Additionally, by malolactic fermentation (MLF), LAB can affect the flavor properties due to compositional changes, including the metabolism of amino acids, polyols, hydrolysis of glycosides, and ester synthesis [54]. LAB also has an essential role in the metabolism of unsaturated fatty acids generating precursors of \(\gamma\)-lactones, which supply a sweet and fatty flavor to alcoholic liquors [55]. Finally, other compounds such as terpenids might come from the plant, and many others are produced during the cooking process [53]. Higher alcohols play an important role in the flavor of fermented beverages; in our study, C5 and C8 alcohols were abundant in fermented sold must. In particular, the identification of 3-methylbutan-1-ol (banana, pungent, and pear attributes) and octan-1-ol (fresh and green leaves attributes) was performed (Table 1). Other alcohols identified were 3,4-dimethylpentan-1-ol and 2-methylpropan-1-ol, which exhibit petrol and ethereal-winey aroma qualities, respectively. The occurrence of these metabolites was due to the activity of yeasts, amino acids in the substrate, and environmental conditions [62]. Yeasts produce fused alcohols from \(\alpha\)-keto acids through the metabolism of amino acids by the Ehrlich pathway, thus branched-chain alcohols such as 3-methylbutan-1-ol, detected in sold must could be produced after the degradation of the branched-chain amino acid leucine [63]. Thus, it is important that, as with the _Saccharomyces_ species and environmental conditions, the amounts and the types of amino acids present in the sold must affect the production of higher alcohols that exhibit different aroma characteristics [63; 64]. Figure 3: The relative abundance of volatile compounds among different chemical classes in fermented sold (_Dasylirion_ sp.) must at different days of the process.