## 3 Results and Discussion
### GC-MS Analysis
In turn, compounds on the right side of principal component PC1 well describe the _Arabica_ species from Ethiopia, Guatem, and Costa Rica (Figure 2(b)). The higher content of butan-2-one, 2-methylpirimidine, and 4.6-dimethylpyrimidine in the odor profile of the three coffees in comparison with the coffees from Brazil and Peru should be highlighted. Pyrimidines are organic volatile compounds from the group of heterocyclic aromatic compounds with a structure similar to pyridine. They are responsible for an unpleasant bitter smell as well as the aroma of hazelnuts, vegetable butter, and caramel. In general, their amount in coffee is correlated with the degree of roasting [21], although its level in the present study was the same in all coffee types. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Name of Compounds**} & \multirow{2}{*}{**Rtime *} & \multicolumn{6}{c}{**Country of Origin**} \\ \cline{4-7}  & & & **Brazil,** & **Ethiopia,** & **Guatemala,** & **Costa Rica,** & **Peru,** \\  & & & **\%** & **\%** & **\%** & **\%** & **\%** \\ \hline
1 & 2-Buten-1-ol & 1.10 & 1.7 & 2.1 & 2.5 & 2.3 & 2.2 \\
2 & 2-oxopropanol & 1.17 & 14.1 & 3.0 & 8.6 & 10.0 & 16.4 \\ Methyl-D3 & & & & & & & \\
3 & 1-diderteo-2-propenyl ether & 1.35 & 6.3 & 11.4 & 8.3 & 7.7 & 6.1 \\
4 & Acetalaldechyde & 1.45 & 4.9 & 8.5 & 3.4 & 4.9 & 5.9 \\
5 & Pirydine & 1.76 & 28.7 & 15.8 & 15.4 & 13.5 & 21.9 \\
6 & Butan-2-one & 2.31 & 6.6 & 10.3 & 8.3 & 9.9 & 7.0 \\
7 & 2-methylpirimidine & 2.54 & 2.9 & 9.3 & 10.8 & 10.5 & 7.7 \\
8 & 2-furrancarboxaldehyde & 2.64 & 10.9 & 10.6 & 7.1 & 7.8 & 5.7 \\
9 & 2-furanmethanol & 2.92 & 5.5 & 8.1 & 7.9 & 8.4 & 7.7 \\
10 & Acetic acid ethenyl ester & 3.16 & 3.2 & 3.5 & 3.9 & 3.8 & 4.2 \\
11 & 4.6-dimethylplyrimidine & 4.25 & 5.5 & 6.2 & 7.6 & 6.8 & 4.4 \\
12 & 2-pethylpyrazine & 4.35 & 2.5 & 2.4 & 3.3 & 3.1 & 1.8 \\
13 & Cis-ocimene & 4.87 & 0.1 & 0.0 & 0.1 & 0.1 & 0.0 \\
14 & 5-methylfuran-2-carbaldehyde & 5.78 & 1.7 & 3.2 & 3.7 & 3.8 & 2.6 \\
15 & 2-furylmethyl acetate & 6.91 & 2.3 & 2.2 & 3.4 & 3.5 & 3.5 \\
16 & N.N-dimethylpyridyn-4-amine & 7.06 & 1.4 & 1.6 & 2.8 & 2.0 & 1.5 \\
17 & 1-methyl-2-cyano-2-piperidine & 7.23 & 0.9 & 1.4 & 2.5 & 1.8 & 1.3 \\
18 & 2.5-dimethyl-3-ethylpyrazine & 9.73 & 0.6 & 0.3 & 0.3 & 0.1 & 0.0 \\
19 & Heptalsioxan & 34.36 & 0.3 & 0.2 & 0.3 & 0.1 & 0.2 \\  & Sum, \(\Sigma\) (\%) & & 100 & 100 & 100 & 100 & 100 \\ \hline \hline \end{tabular}  
*–retention time.  
\end{table} 
Table 1: Chemical compounds detected in all _Arabica_ coffees from: Brazil, Ethiopia, Guatem, Costa Rica, and Peru. Figure 4a shows the projection of the variables of the major groups of chemical compounds on the PC1 and PC2 plane. As in the case of the volatile compounds, all chemical groups except \"others\" (Figure 2) differentiated coffee according to the origin. The group of azines and acids were the most abundant volatile substances in the coffees from Brazil and Peru. This relationship is described by principal component PC1 (Figure 4a,b). In turn, the higher contents of alcohols, ketones, and hydrazides detected in the volatile compound profiles of the coffees from Ethiopia, Guatem, and Costa Rica differentiated these beans from the Brazilian and Peruvian coffees by the first principal component as well. A similar relationship for the analyzed volatile chemicals is shown in Figure 3a,b. The chemometric analysis indicates that the coffee species maintain their specific odor profile, which is usually determined by four dominant groups of volatile compounds [24].