## 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\({}^{\star}\)** \\ \hline Undecanal & 112-44-7 & [51] & Sweet, fatty, orange and rose undertone & [36] \\ Dodecanal & 112-54-9 & [49,51] & Fatty, violet-like & [36] \\ \hline _Aronatics_ & & & \\ \hline Benzaldehyde & 100-52-7 & [33] & Sweet, bitter almond-like, bitter & [34,36,41] \\ Benzeneacetaldehyde & 122-78-1 & [33] & Pungent-green, hyacinth-like, floral, sweet-fruity, & [34,36,39,50,52] \\
2-Hydroxybenzaldehyde & 90-02-8 & [33] & Hunger, herbaceous, spicy-floral, bitter, almond-like & [34,36] \\
2-Methylbenzaldehyde & 529-20-4 & [33] & Sweet, beauty, fresh pea & [34,37] \\
2-Phenyi-2-butrenal & 4411-89-6 & [33] & Musty, floral, cocoa & [4] \\ \hline _Esters_ & & & \\ \hline _Aliphatics_ & & & \\ \hline Methyl acetate & 79-20-9 & [33] & Sweet, ethereal, fruity & [34,36] \\ Methyl! propenoate & 96-33-3 & - & - \\ Methyl! propenoate & 554-12-1 & [33] & Ethereal-rum-like, sweet, fruity & [34,36] \\ Methyl! glycolate & 96-35-5 & [47] & & \\ Methyl! 2-methylpropenoate & 80-62-6 & Acid, fruity & [36] \\ Methyl! butanoate & 623-42-7 & [33] & Sweet-ethereal, fruity, apple peel, peach-like & [34,36] \\ Methyl! 2-butreonate & 18707-60-3 & [48] & - & \\ Methyl! 2-methylbutanoate & 868-57-5 & Sweet, fruity, apple-like & [36] \\ Methyl! 3-methylbutanoate & 556-24-1 & [33] & Ethereal, fruity, apple-like, herbaceous & [34,36] \\
3-Methyl! formate & 110-45-2 & [37] & Plum, fruity, fluck currant-like & [36,37] \\ Butyl acetate & 123-86-4 & [33] & Pear-like, ethereal, fruity, ripe/over-ripe fruits-like & [34,36] \\ Methyl! pentanoate & 624-24-8 & [33] & Ethereal, green-fruity, apple-like, pineapple-like & [34,36] \\ Methyl! 3-methyl?-boutenoate & 924-50-5 & [53] & Fruity, apple-like & [54,36] \\ Ethyl 3-methylbutanoate & 108-64-5 & [33] & Fruity, apple-like & [36,38,41] \\ Isoamyl acetate & 123-92-2 & [33] & Fruity, banana, sweet, apple-like & [34,36] \\ Methyl! 3-methylprotonanoate & 2177-78-8 & - & - & \\ \(3\)-Methyl!-3-butrely-3-butrely acetate & 5205-07-2 & - & - & \\ Methyl! 4-methylly/pentanoate & 2412-80-8 & Sweet, pineapple-like & [36] \\ Pentyl acetate & 628-63-7 & - & - & \\ Methyl hexanoate & 106-70-7 & [33] & Pineapple-like, aptoro-like, sweet, ethereal & [34,36] \\ Ethyl triplicate & 5837-78-5 & - & - & \\
3-Methyl!-2-butrely acetate & 1191-16-8 & [33] & Fresh, fruity, banana-like, bergamot-like & [34] \\ Heyl formate & 629-33-4 & Fruity, apple-like, unripe-plum & [36] \\ Ethylidene acetate & 542-10-9 & - & - & \\ Methyl! 4-Methyl!-2-cowpentanoate & 3682-43-7 & - & - \\ butyl! 2-methyl?-2-propenoate & 97-88-1 & - & - \\ Heyl acetate & 142-92-7 & [55] & Fruity, apple, cherry, pear, floral & [36] \\ Isobutyl 3-methyl?-2-butenoate & 3043-54-9 & - & - \\ Methyl octanoate & 111-15- & - & Winy, fruity, orange-like & [36] \\
3-Methylbutyl 3-Methyl!-2-butenoate & 56922-73-7 & - & - & \\ Methyl decanoate & 110-42-9 & - & - \\ Methyl dodecanoate & 111-82-0 & Fatty, floral, wine-like & [36] \\ \hline _Aronatics_ & & & \\ \hline \hline Phenyl acetate & 122-79-2 & [56,57] & Floral, rosy, dark chocolate-like & [4] \\ Benzyl formate & 104-57-4 & [33] & Fruity, green, herbaceous, earthy, floral & [34,36] \\ Methyl benzoate & 93-58-3 & [33] & Fruity, cananga-like & [36] \\ Methyl phenylacetate & 101-41-7 & [33] & Honey, musky, jasmine, floral & [34,36] \\
2-Phenyleth formate & 104-62-1 & [33] & Green, herbaceous, rosy, hyacinth, chrysanthemum, & [34,36] \\ Methyl! 2-hydroxybenzoate & 119-36-8 & [33] & Sweet, rooty-fruity, minty, spicy, wintergreen-like & [34,36] \\
2-Phenyleth acetate & 103-45-7 & [58] & Floral, rose, honey-like & [36] \\ Ethyl 2-hydroxybenzoate & 118-61-6 & [48] & Wintergreen & [36] \\ \hline \hline \multicolumn{4}{c}{**Furan compounds**} \\ \hline Furan & 110-00-9 & [33] & Spicy-smoky, cinnamon-like & [34] \\
2-Methylfuran & 534-22-5 & [33] & Ethereal, sickly & [20] \\ Tetrahydrofuran & 109-99-9 & [33] & Sweet-gassy, bread-like & [34] \\
2-5-Dimethylfuran & 625-65-6 & [33] & coffee & [20] \\
2-4-Dimethylfuran & 3710-43-8 & [48] & - & \\
2-Propylfuran & 429-91-8 & [33] & - & \\
2-Ethyl?-5-methylfuran & 1703-52-2 & [33] & - & \\
2-Ethyl-5-methyltetrahydrofuran & 931-39-5 & - & - & \\
2-Paramcarbonitrile & 617-90-3 & & - & \\ Dihydro?-2-methyl?-3-furanone & 318-00-9 & [33] & Bread-like, buttery, nutty & [20,36] \\
2,3-5-Timethylfuran & 10504-04-8 & [33] & - & \\
3-Furaldehyde & 498-60-2 & [33] & - & \\
2-Vinyl\(5\)-methylfuran & 10504-13-9 & [33] & Coffee & [20] \\ \hline \end{tabular}
\end{table}