# Analysis of Volatile Compounds in Coffee Prepared by Various Brewing and Roasting Methods
## 3 Results  
### Analysis of Volatile Compounds in Coffee  
The selected 24 volatile compounds are shown in Table 1. These selected volatile compounds are the main volatiles identified in coffee samples. In addition, these 24 volatiles were analyzed the most in our study and represent the aroma's functional groups (chemical types) in coffee. Identification of the volatile compounds was based on their RI, co-injection, and comparison of their mass spectrum with those in the Wiley mass spectrum database. All values are represented as the peak area ratio (peak area of each peak/peak area of internal standard). Table 2 shows the peak area ratio of the volatile compounds in E-1 to E-9 (espresso roasted at 235 \({}^{\circ}\)C for 13 min) and C-1 to C-9 (cold brew roasted at 235 \({}^{\circ}\)C for 13 min). Among the espresso coffees, the finest grinds (355 \(\upmu\)m) produced significantly higher measured GC/MS intensities of all 24 volatile compounds, except for 2,2\({}^{\prime}\)-[oxybis (methylene)]bis-furan and 2-methoxy-4-vinylphenol, compared with the medium (500 \(\upmu\)m) and large (750 \(\upmu\)m) grind sizes (\(p<0.05\)). For espresso coffees extracted with different types of water, bottled water and tap water led to high measured GC/MS intensities of all 24 volatile compounds. Comparing cold brew coffees, fine grinds (355 \(\upmu\)m) resulted in significantly high measured GC/MS intensities of volatile compounds, respectively (\(p<0.05\)). For cold brew coffees (C-1 to C-9), filtered water led to significantly higher measured GC/MS intensities of volatile compounds (\(p<0.05\)). The water used in this study has different amounts of carbonates and bicarbonate. The levels of carbonates and bicarbonate were much lower in the filtered water compared to the bottled and tap water. A study by [PERSON] (1958) showed that the carbonates and bicarbonate of sodium ions slowed down the brewing time. Therefore, cold brew, which is extracted by soaking coffee beans in water,appears to have been more affected by the extraction of volatile compounds than _espresso_ coffee [12]. Table 3 shows the volatile compounds in both types of coffee roasted at 240 \({}^{\circ}\)C for 15 min. Among the espresso coffees (E-10 to E-18), the smaller particle of ground coffee (355 \(\upmu\)m) corresponded to significantly higher measured GC/MS intensities of volatile compounds (\(p<0.05\)). Among the espresso coffees extracted with different types of water (E-10, E-11, and E-12), filtered water resulted in significantly higher measured GC/MS intensities of 18 volatile compounds (\(p<0.05\)). Comparing E-13, E-14, and E-15, the measured GC/MS intensities of 22 volatile compounds, excluding 2-methylpyrazine and furfuryl alcohol, were notably high when filtered water was used (\(p<0.05\)). Comparing E-16, E-17, and E-18, tap water led to significantly higher measured GC/MS intensities of 21 volatile compounds (\(p<0.05\)). Comparing cold brew samples, fine girnds (355 \(\upmu\)m) occasioned notably high levels of volatile compounds, respectively (\(p<0.05\)). Among C-10 to C-12, the measured GC/MS intensities of all 24 volatile compounds were similarly detected. Among C-13 to C-15 and C-16 to C-18, filtered water gave rise to remarkably high measured GC/MS intensities of 19 and 2 volatile compounds, respectively (\(p<0.05\)). For extraction with filtered water, more volatiles could be expected to be detected as grind size decreases and roasting temperature increases. However, in this study, espresso prepared from filtered water and at a relatively low roasting temperature did not generate a high concentration of volatiles. Similarly, cold brew prepared from fine girnds and filtered water did not have a high concentration of volatiles. The reason for this result should be examined in future studies.