## 3 Results and Discussion
### Volatile Composition of Single-Dose Espresso Coffee-Based Blends
\begin{table}
\begin{tabular}{c c c c c} \hline
**Compound** & **CAS Number** & **Reported \({}^{\star}\)** & **Aroma Descriptor \({}^{\text{b}}\)** & **References \({}^{\text{c}}\)** \\ \hline _Aronatics_ & & & & \\ \hline Acetophenone & 98-86-2 & [33] & Sweet & [36] \\ 1-Phenryl-2-propanane & 103-79-7 & & - & - \\ \(\circ\)-Hydroxacetophenone & 118-93-4 & [33] & Sweet, heavy-floral, herbaceous, new-known hay-like, & [34] \\ 1-Phenryl-1-2-propanadiene & 579-07-7 & [33] & Warm-floral, herbaceous, plastic & [34,36] \\ \(\circ\)-Methylxacetophenone & 122-00-9 & & - & \\ 1-Phenryl-2-butanone & 1007-32-5 & & - & \\ 1-(4-Hydroxyphenyl)-1-propanane & 70-70-2 & & - & \\ 4-Hydrox-3-methylxacetophenone & 876-02-8 & [64] & - & \\ \hline \multicolumn{4}{c}{**Volatile phenols**} & & \\ \hline
2-methoxyphenol (Guaiacol) & 90-05-1 & [33] & Smoke-like, phenolic, burnt, spicy, woody, meaty, sweet & [20,35,39,44, 60] \\ 2.6-Dmmethylphenol & 576-26-1 & [33] & Ground-cofee, phenolic & [50,66] \\ 2-Alylphenol & 1745-81-9 & & - & \\ 4-Ethyl-2-methoxyphenyl (4-Ethylguaiacol) & 2785-89-9 & [33] & Smokoly, clove-like, spicy, burnt, vanilla-like, sweet, & [20,36,39,44,60] \\ \(\circ\)-Methody-4-vinylphenol (4-Vinylguaiacol) & 7786-61-0 & [33] & Spicy, clove-like, phenolic, apple, rum, roasted peanut & [20,34,36,39,44,60] \\ \hline \multicolumn{4}{c}{**Oxazoles**} & & \\ \hline
4-Methylxazole & 693-93-6 & & - & \\
4-5-Dimethylyoxazole & 20662-83-3 & [33] & - & \\ Trimethyloxazole & 20662-84-4 & [33] & - & \\
4-Ethyl-2-5-dimethylyoxazole & 30408-61-8 & [33] & - & \\
2-Ethyl-4-methyl-5-propylyoxazole & 102586-53-8 & & - & \\
4,5-Dimethyl-2-propylxazole & 53833-32-2 & [33] & - & \\
4,5-Dimethyl-2-isobutyyloxazole & 26131-91-9 & & - & \\ Benzoxazole & 273-53-0 & [33] & Sweet, gassy-pungent, floral-sweet, tobacco & [34,60] \\ \hline \multicolumn{4}{c}{**Pyazines**} & & \\ \hline Pyrazine & 290-37-9 & [33] & Pungent, sweet, floral, coffee & [20,34,54] \\ Methylyrazine & 109-08-0 & [33] & Nutty, cocoa, green, roasted, chocolate, meaty, toasted & [20,34,54] \\
2,5-Dimethylpyrazine & 123-32-0 & [33] & Chocolate, roasted nuts, earthy, grassy, roasted, nutty & [36,54,60] \\
2-Ethylpyrazine & 13925-00-3 & [33] & Peanut butter, mustty, nutty, woody, buttery, roasted, & [36,60] \\
2,3-Dimethyllyrazine & 5910-89-4 & [33] & Nitty, cocoa-like odor, green note, toasted, roasted & [20,36,54] \\ Vinylyrazine & 4177-16-6 & [33] & - & \\
2-Isopropyl-2-Isopropyl-2-3 & [33] & Toasted, flowery, fruity, hazelnut-like & [2,20,54] \\
2-Ethyl-3-methylyrazine & 15707-23-0 & [33] & Raw-potato, roasted, earthy, nutty, peanut-like, & [20,36,54] \\ 2-Propylyrazine & 18138-03-9 & [33] & Green, vegetable, herbal & [2,36] \\ 2-Vinyl-6-methylyrazine & 13925-09-2 & [33] & Coffee & [20] \\ Acetylpyrazole & 22047-25-2 & [33] & Tousted & [20] \\
2-Methyl-3-isopropylpyrazole & 15986-81-9 & - & - & \\ Isoupplyyrazine & 29460-922-2 & & - & \\ Isopropylpyrazine & 3871-41-6 & [33] & Toasted, potato-like, roasted & [2,20,54] \\
2,6-Diethyllyrazine & 13067-27-1 & [33] & Vegetable-like, earthy, bell pepper, raw potato, & [36,38,39,60] \\
2-Isopropyl-3-methoxyyrazine & 25773-40-4 & [33] & Salmon, roasty, peasy & [36,83,39,60] \\
6,7-Dihydro-5H-cyclopentyrazine & 23747-47-9 & [33] & Green, phenolic, nutty, roast & [35,60] \\
2-Acetyl-3-methylyrazine & 23787-80-6 & [33] & Cereral, roasted bean, roasted, nutty, & [36,60] \\
2-Isobutyl-3-methylyrazine & 13925-06-9 & [33] & - & \\
5H-5-Methyl-6-7-dihydroxycyclopentyrazine & 23747-48-0 & [33] & Earthy, baked potato, peanut, roasted, nutty & [35,36,60] \\
2-Methyl-4-(1-propyl)yrazine (isomer) & 104638-11-1 & [33] & Nutty, meaty, roasted & hazelnut, earthy, roasty & [35,36,44,45,52] \\
2-Acetyl-3-ethylpyrazole & 32574-92-8 & [29] & - & \\
2-Isonymlyrazine & 40709-22-5 & & - & \\
2-Isonymly-3-isopropylrazine & 24683-00-9 & [33] & Green bell- pepper note, galbanum oil, red pepper, & [4,36,44,60] \\
2-Burryl-3-methylypyrazole & 15987-00-5 & [33] & - & \\
2-Dimethyl-3-isobutyylpyrazole & 32736-940 & [33] & - & \\
1-Methyly(1,2-a)pyrazine & 64608-59-9 & [33] & - & \\
6,7-Dihydro-2-5-dimethyl-5H- & 38917-61-2 & [33] & - & \\ cyclopentoxyrazine & 2.5-Methyl-3-6-dimethyl-pyrazine & 18903-30-5 & [33] & - & \\
2-Methyl-16-isopentyrazine & 91010-41-2 & - & - & \\
2-Dimethyl-3-methyl-1-butylpyrazine & 56617-00 & - & - & \\
2-Dimethyl-3-isomanylyrazine & 18433-98-2 & - & - & \\
2-3-Dimethyl-5-isopentypyrazole & 18450-01-6 & - & - & \\ \hline \end{tabular}
\end{table}