## 3 Results and Discussion
### Chemical Analysis of the Fermentation Liquid Fraction and Coffee Beans  
The sugar consumption profile and metabolic formation showed the activity of the initial cultures used during the fermentation process. Glucose and fructose were consumed during fermentation and transformed mainly into lactic acid (associated with the metabolism of _P. acidilactici_ LPBC161) and ethanol (associated with the metabolism of _P. fermentans_ YC5.2) as shown in Table 1. It is possible to observe a decrease in sugars (glucose and fructose) during the 24 h of fermentation (Table 1). Both glucose and fructose were partially consumed until the end of the process. During the fermentation process, sugars were used for microbial growth and a significant amount of ethanol and lactic acid were produced, causing a drop in pH (5.16 to 4.13). The reduction of pH levels below 4.5 is a method widely used by coffee producers to determine the end of the fermentation of coffee beans during the wet processing method [11; 35]. In addition, in conjecture with organic acid production, ethanol generation inhibits the growth of undesirable microorganisms during the fermentation process. HPLC analysis of the liquid fermentation fraction revealed the high presence of lactic acid and ethanol. These compounds were associated with LAB and yeast metabolism, respectively. Lactic acid was the main organic acid produced, reaching a concentration of 1.41 g/L at 24 h (Table 1). This primary metabolite is mainly produced by the central carbon metabolism of homofermatterative LAB [35]. The diffusion of acids in the grains can influence the flavor and final quality of the beverage [13; 17]. Lactic acid is known to attribute desirable lactic sensory notes and contribute to the acidity and body of the final drink [15]. Ethanol showed a constant increase throughout fermentation (0.8 g/L), indicating a high metabolic activity of non-_Saccharomyces_ yeasts [8]. Among the volatiles, GC-MS analyses identified nine compounds, two higher alcohols, four esters and three aldehydes (Table 1). Ethyl acetate was the most abundant compound formed during fermentation. _P. fermentans_ YC5.2 was selected based mainly on the production of this metabolite, which plays an important role in the development of aroma for coffee beans [13]. The diffusion and persistence of ethyl acetate in the grain contributes to the development of desirable fruit notes and nuances of grape/cherry in the coffee \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Compound** & **0 h** & **8 h** & **19 h** & **24 h** \\ \hline GC-MS (area) & & & & \\ _Higher alcohols_ (**2**) & & & & \\ _1-Butanol, 3-methyl_ & 0.27 \(\pm\) 0.02 a & 0.39 \(\pm\) 0.02 b & 0.63 \(\pm\) 0.00 c & 0.60 \(\pm\) 0.00 c \\ _2-Heptanol_ & 0.17 \(\pm\) 0.01 a & 0.13 \(\pm\) 0.00 a & ND & ND \\ _Ester_ (**4**) & & & & \\ _Ethyl acetate_ & 4.10 \(\pm\) 0.13 a & 2.24 \(\pm\) 0.78 b & 3.05 \(\pm\) 0.10 c & 4.80 \(\pm\) 0.02 a \\ _Methyl acetate_ & ND & ND & 3.80 \(\pm\) 0.41 a & 0.49 \(\pm\) 0.04 b \\ _Ethyl isobutyrate_ & ND & ND & 0.63 \(\pm\) 0.00 & ND \\ _Isamyl acetate_ & ND & 0.25 \(\pm\) 0.00 a & 0.37 \(\pm\) 0.08 a & 0.27 \(\pm\) 0.00 a \\ _Aldehyde_ (**3**) & & & & \\ _Butanal, 3 methyl_ & 0.86 \(\pm\) 0.06 a & 0.78 \(\pm\) 0.05 ab & 0.21 \(\pm\) 0.00 b & 0.74 \(\pm\) 0.28 ab \\ _Butanal, 2 methyl_ & 0.63 \(\pm\) 0.26 a & 0.34 \(\pm\) 0.00 a & 0.13 \(\pm\) 0.01 a & 0.32 \(\pm\) 0.00a \\ _Benzenacetaldehyde_ & 0.23 \(\pm\) 0.02 a & 0.33 \(\pm\) 0.10 a & ND & ND \\ \hline HPLC (g/L) & & & & \\ _Glucose_ & 1.08 \(\pm\) 0.11 a & 0.75 \(\pm\) 0.09 ab & 0.52 \(\pm\) 0.14 b & 0.62 \(\pm\) 0.21 b \\ _Fructose_ & 2.52 \(\pm\) 0.22 a & 1.78 \(\pm\) 0.49 b & 1.26 \(\pm\) 0.13 b & 1.47 \(\pm\) 0.06 b \\ _Lactic acid_ & ND & 0.43 \(\pm\) 0.04 a & 1.24 \(\pm\) 0.21 b & 1.41 \(\pm\) 0.12 b \\ _Ethanol_ & ND & 0.37 \(\pm\) 0.12 a & 0.50 \(\pm\) 0.09 a & 0.81 \(\pm\) 0.08 b \\ pH & 5.16 & 4.50 & 4.17 & 4.13 \\ \hline \hline \end{tabular}
\end{table}