## 3 Results and Discussion
### Evaluation of the Effect of Yeast Starter Cultures on the Volatile Compound Profile
In addition to the starter cultures influencing the volatile profile, differences in this variable were also observed between the coffee varieties studied. This variation may be linked to genetic differences in the coffee varieties used [50]. The CP coffee variety was able to accumulate specific compounds, such as 1-ethylpyrrole, 2-formylpyrrole, 1-furfurylpyrrole, and hexadecanoic acid (Figure 5G), which promoted the formation of fresh notes, vegetables, and a full-bodied toast. It was also possible to observe this behavior for the CA62 and P2 coffee variety, where 2-formylpyrrole was the only compound that was present in this variety and could bring out roasted and nutty notes, contributing to the construction of a coffee drink in the nutty and cocoa category (Figure 5F) [51]. When _K. lactis_ B10 was used in the fermentation of the green beans, the roasted beans had greater uniqueness than _S. cerevisiae_ CA11. This was due to the volatile compound precursors present at the end of fermentation, which were biotransformed to individualize the coffee varieties. The conversion of aldehyde starter cultures into higher alcohols after fermentation, through the activity of alcohol dehydrogenases, made it possible for this chemical group to be more abundant in the P2 (43.77%) and CP (41.50%) varieties [52]. This predominance is mainly due to furfuryl alcohol, constituting 39.62% of the P2 variety and 37.62% of CP. Furfuryl alcohol provides sweet and mild caramel notes to coffee (Figure 4A) [48]. The furans, in turn, were represented mainly by the presence of 5-hydroxymethylfurfural, which was greater in variety A when _K. lactis_ B10 was used for fermentation (8.92%). The furfural content ranged between 0.23% (A) and 14.74% (CP), so its maximum predominance depended on the coffee variety and use of the starter culture. These compounds reinforce coffee's sweet, woody, almond, and roasted flavors and are classified in the sweet category on the flavor wheel [51]. The content of pyrazines presented a variation of 6.69-18.70% among the studied coffee varieties. These compounds are mainly derived from [PERSON]'s degradation of \(\alpha\)-amino acids during roasting. Seven pyrazines were found in the coffee samples fermented with _K. lactis_ B10. The coffee variety A fermented by _K. lactis_ B10 was the one with the higher content of pyrazines. Here, methylpyrazine (11.96%) had the greatest abundance among the identified pyrazines. All of them are considered potent coffee odorants, characterized by notes of nutty, cocoa, and roasted odors and, consequently, classified in the nutty/cocoa category [13; 51]. Pyridines, pyrroles, and phenols were identified in all treatments and were less dominant, although their abundance was greater when starter cultures were present (Figure 5A). Considering the individuality of fermentations in the presence of starter cultures, it was observed that of the 100 compounds identified, some volatiles were only present when starter cultures were used due to the production of secondary metabolites during fermentattion, which can migrate to the beans and improve flavor [31] (Figure 5). 5-Methyl-2-furfuryl alcohol and n-hexadecanoic acid were produced exclusively in the presence of yeasts. Regarding fermentation using _S. cerevisiae_ CA11, of the 22 common compounds, only CP exhibited the unique compound hexadecanoic acid (Figure 5C). This compound constitutes the lipid fraction of coffee, so its presence after roasting results from the fermentation of green coffee, the transesterification of triglycerides containing palmitic acid with ethanol, or the direct esterification of free palmitic acid with ethanol. This compound can impart fatty and sour nuances, forming part of the sour/fermented category [50; 51]. In contrast to the use of _S.