# Analysis of Volatile Compounds in Coffee Prepared by Various Brewing and Roasting Methods
## 3 Results
### Analysis of Volatile Compounds in Coffee
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **Compounds** & **Retention Time** & **R.I** & **R.I (Ref)** &
\begin{tabular}{c} **Co-** \\ **Injection** \\ \end{tabular} & **Mass Spectrum** \\ \hline a1 & 2-Methylpyrazine & 25.99 & 1289 & 1288 & o & o \\ a2 & 2,3-Dimethylpyrazine & 29.87 & 1370 & 1371 & o & o \\ a3 & 2,5-Dimethylpyrazine & 28.73 & 1346 & 1348 & o & o \\ a4 & 2,6-Dimethylpyrazine & 29.02 & 1352 & 1354 & o & o \\ a5 & 2-Ethpypyrazine & 29.23 & 1356 & 1359 & o & o \\ a6 & 2,6-Dietibpyrazine & 33.83 & 1456 & 1444 & & o \\ a7 & 2-Ethyl-3-methylpyrazine & 32.54 & 1427 & 1422 & o & o \\ a8 & 2-Ethyl-5-methylpyrazine & 31.64 & 1407 & 1415 & & o \\ a9 & 3-Ethyl-2,5-dimethylpyrazine & 34.32 & 1467 & 1452 & o & o \\ a10 & Isopropenyl pyrazine & 40.82 & 1619 & & & o \\ \hline b1 & 2-Acetylfuran & 36.74 & 1522 & 1527 & o & o \\ b2 & 2,2\({}^{\prime}\)-Bifuran & 40.47 & 1610 & 1614 & & o \\ b3 & 2,2\({}^{\prime}\)-Methylenebisfuran & 40.93 & 1622 & 1615 & & o \\ b4 & 2,2\({}^{\prime}\)- & & & & & \\ \hline b5 & Furfuryl alcohol & 42.84 & 1669 & 1666 & o & o \\ b6 & Furfuryl acetate & 37.82 & 1547 & 1552 & o & o \\ b7 & Furfuryl propionate & 40.36 & 1607 & 1603 & o & o \\ b8 & Furfural & 34.81 & 1477 & 1482 & o & o \\ b9 & 5-Methylfurfural & 39.63 & 1590 & 1596 & o & o \\ \hline c1 & 1-Methylpyrrole & 19.30 & 1147 & 1140 & o & o \\ c2 & 1-Furfurylpyrrole & 49.66 & 1841 & 1833 & o & o \\ \hline d1 & Guaiocal (2-Metoxyphenol) & 51.10 & 1874 & 1872 & o & o \\ d2 & 4-Ethylguaiacol & 59.93 & 2052 & 2054 & o & o \\ d3 & 2-Metoxy-4-vinylphenol & 64.80 & 2156 & o & o \\ \hline \hline \end{tabular} Identification for volatile compounds compared with Retention Index (RI) on DB-WAX column in NIST and VCF library, co-injection, and mass spectrum.  
\end{table} 
Table 1: Volatile compounds in coffee (E-1: espresso brewing method, roasted at 235 \({}^{\circ}\)C for 13 min, particle size of ground coffee bean 355 \(\upmu\)m, and purified water). Table 4 lists the volatile compounds in both types of coffee roasted at 245 \({}^{\circ}\)C for 17 min (E-19 to E-27 and C-19 to C-27). Comparing expresso coffee samples, fine grinds (355 \(\upmu\)m) led to significantly high measured GC/MS intensities of volatile compounds, respectively (\(p<0.05\)). Among E-19 to E-21, filtered water led to slightly but not significantly high measured GC/MS intensities of all 24 volatile compounds (\(p>0.05\)), except for isopropenyl pyrazine, 2,6-diethylpyrazine, and 2-methoxy-4-vinylphenol. Among E-22 to E-24 and E-25 to E-27, filtered water resulted in significantly high measured GC/MS intensities of 6 and 18 volatile compounds, respectively (\(p<0.05\)). Comparing cold brew samples, there were no or highly significant differences in grind sizes 500 and 710 \(\upmu\)m. Filtered water occasioned significantly high measured GC/MS intensities of 1-furfurylpyrrole and 2-methoxy-4-vinylphenol among cold brews C-19 to C-21 (\(p<0.05\)), furfuryl alcohol among cold brews C-22 to C-24 (\(p<0.05\)), and 12 volatile compounds among cold brews C-25 to C-27 (\(p<0.05\)). Comparing volatile compounds of middle size (500 \(\upmu\)m) of ground coffee, the levels of 2-methylpyrazine, 2,5-Dimethylpyrazine, 2,6-Dimethylpyrazine, 2-ethyl-5-methylpyrazine, 3-ethyl-2,5-dimethylpyrazine, 2-acetylfuran, 2,2\({}^{\prime}\)-Bifuran, 5-Methylfurfural, and 1-methylpyrrole in cold brew coffee were higher than espresso coffee. These flavor compounds have a sweet, nutty, and fruity odor [23; 24; 25; 26]. In Figure 1, among the many volatile compounds analyzed, significantly increased or decreased compounds were selected to show their levels. As shown in Figure 1a, increasing the roasting temperature and time increased the levels of 2,2\({}^{\prime}\)-methylene-bisfuran, guaiacol, and 4-ethylguaiacol (\(p<0.05\)), and decreased the levels of furfural and 5-methylfurfural (\(p<0.05\)). In [PERSON] and [PERSON]'s (2009) study, intensifying the roasting conditions of green coffee beans yielded relatively lower furanone derivatives and furfural.