## 3 Results and Discussion
### Evaluation of the Effect of Yeast Starter Cultures on the Volatile Compound Profile  
The complexity of coffee flavor is mainly attributed to volatile compounds, which may be inherent to the coffee beans, as well as microbial metabolites resulting from the fermentation process [9; 42]. Based on their odor quality, they can be classified into nine main odorant groups: (i) roasted, (ii) spicy, (iii) nutty/cocoa, (iv) sweet, (v) floral, (vi) fruity, (vii) acidic/fermented, (viii) green/vegetative, and (ix) other (including chemical and paper/mold odors). These are represented in the Specialty Coffee Association's (SCA) Coffee Taster's Flavor Wheel based on the World Coffee Survey's Sensory Lexicon [1; 43]. A total of 100 volatile compounds were detected in green and roasted coffee using SPME/GC-MS (Supplementary Material--Tables S3-S6). These compounds were grouped into 13 chemical classes: aldehydes (20), alkanes (9), ketones (6), phenols (1), alcohols (19),esters (10), furans (7), pyrazines (7), pyrroles (4), free fatty acids (FFA/acids) (9), pyridines (1), lactones (2), and other compounds (5) (Figure 5). The starter cultures altered the profile of volatile compounds. In addition, the profile differed depending on the coffee variety evaluated. After fermentation (48 h), aldehydes predominated in green coffee, and the highest abundance was observed in coffee variety A (73.63%) and CP when subjected to fermentation by _S. cerevisiae_ CA11. This behavior occurred probably due to the intense catabolism of sugars during the fermentation of these coffee varieties in the presence of _S. cerevisiae_ CA11, as noted in Section 3.3 of this text (Figure 4B). The abundance of aldehydes decreased during fermentation, drying, and roasting, which indicates that processing influenced the volatile profile. In addition, using different metabolic pathways, the starter cultures contributed to the biotransformation of these compounds present in green coffee, which consequently enabled the production of distinct volatile compounds during roasting [30; 44; 45]. The most abundant compound at the end of fermentation was benzeneacetaldehyde, which gave the coffee a green, honey-like aroma. These aromatic nuances are considered green/vegetative and sweet [43; 46]. Still highlighting the compounds in the fermented green coffee varieties, it was observed that esters were abundant only in the CA62 variety when _S. cerevisiae_ CA11 was  
Figure 5: Heatmap of chemical classes of volatile compounds and grouping of coffee cultivars fermented using different inoculants (**A**): (48 h, dry and roasted). Venn diagram of volatile compounds as a function of inoculation and roasted coffee variety. **(B)**: N; **(C)**: CA11; **(D)**: B10; **(E)**: CP; **(F)**: P2; **(G)**: CA62; **(H)**: A.  
used as the starter culture. The presence of this chemical class is due to ester production through the metabolism of carbon and nitrogen during fermentation [47]. The roasting process triggers biochemical reactions that provide flavor and aroma to roasted coffee. The most predominant chemical classes in the roasted coffee varieties were alcohols, pyrroles, furrans, phenols, and pyridines. Flavonoids such as furfurrals, pyrazines, and pyrroles originate from the Maillard reaction through the precursors 3-deoxyosome and furrans in the caramelization of sugars [48]. Natural fermentation resulted in 19 compounds common to all the roast coffee varieties evaluated. However, it was possible to observe that some compounds may be present exclusively depending on the coffee variety observed. Coffee variety A and CA62 have three unique compounds, pyrazine, 3-ethyl-2,5-dimethyl, and corylon, which give this variety nuances of cereals, bread, mushrooms, and potatoes, such as a burnt and toasted appearance. This type of sensory description leads the coffee to be considered a coffee without many sensory expressions (Figure 4B) [49].