# Quantitative Analysis of Caffe in Roasted Coffee: A Comparison of Brewing Methods
## 3 Results and Discussion
### Brewing Methods
#### 3.3.2 Espresso
Factors that may have influenced the results were a higher coffee-to-water ratio [45], higher water temperature [34], the use of a different method for caffeine determination [35], and the use of extraction accessories: filter baskets and perforated discs [41]. However, conducting a more detailed analysis of the effect of individual parameters on caffeine content is hampered by the incompleteness of the data in some studies. In many cases, the brewing time [33; 38; 41; 45; 48; 55] or the amount of water used [30; 41; 53; 55] is not provided, making it impossible to calculate the coffee-to-water ratio. The absence of this crucial information significantly limits the possibility of comparing studies. In contrast, the studies by [PERSON] et al. [56] and [PERSON] et al. [34] used similar parameters (water \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Brewing Parameters**} & \multicolumn{3}{c}{**Caffeine**} \\
**Brewing Time** [s] & **T of Water [\({}^{\circ}\)C]** & **Amount** & **Amount** & **Coffee:Water** **Matio** & **Determination** **Method** & **Caffeine Content** & **Reference** \\ \hline  & & & & & & [mg/100 mL] & \\ \hline
27 & 93 & n.d. & 14 & n.d. & HPLC & 410.00 & [30] \\ \hline n.d. & 93 & 25 & 7 & 28:100 & HPLC & 244.00 & [33] \\ \hline
25 & 92 & 25 & 7.5 & 28:100 & HPLC & 526.80–576.00 (A) & [34] \\ \hline n.d. & 92 & 25 & 7 & 28:100 & HPLC & 248.68 & [38] \\ \hline n.d. & 93 & n.d. & 14 & 50:100 & HPLC & 311.30–576.60 (A) & [41] \\ \hline
30 & 90 & 25 & 7 & 28:100 & HPLC & 47.30–53.50 & [44] \\ \hline n.d. & 92 & 15–53 & 9,18 & n.d. & HPLC & 240.00–700.00 & [45] \\ \hline n.d. & 95–97 & 50 & 7 & 14:100 & HPLC & 97.71 & [48] \\ \hline  & 88–93 & & & & & 174.00 (A) & \\  & 90 & & & & & 256.00 (A) & \\
25 & 88–93 & 25 & 15 & 60–100 & HPLC & 214.00 (A) & [50] \\  & 90 & & & & & 281.00 (R) & \\  & 93–88 & & & & & 245.00 (R) & \\  & 93–88 & & & & & 119.00 (R) & \\ \hline
25–26 & 93 & n.d. & 8 & n.d. & HPLC & 83.90–108.00 & [53] \\ \hline
8–24 & 92 & 25 & 6, 7, 8 & 24–32:100 & HPLC & 320.12–521.44 & [56] \\ \hline  & & & & & & [mg/100 g] & \\ \hline
30 & 90 & 50 & 14 & 28:100 & NMR & 2868.00–3871.00 (A) & [35] \\ \hline n.d. & 79.1–96.5 & n.d. & 20 & n.d. & HPLC & 457.00 & [55] \\ \hline \hline \end{tabular} Abbreviations: A–Arabica; n.d.—no data; HPLC—high-performance liquid chromatography; NMR—nuclear magnetic resonance spectroscopy; R—Robusta; SP—spectrophotometry; T—temperature.  
\end{table} 
Table 6: Espresso method—brewing parameters and caffeine content. temperature and coffee-to-water ratio), but the lack of information on coffee type in one of the studies [56] makes it impossible to draw clear conclusions on the effect of brewing time on the caffeine content of the resulting espresso. The higher caffeine concentrations in the study by [PERSON] et al. [34] may also be due to other factors, not only the coffee type. In one of these studies [55], the results were presented in mass units; therefore, the findings from this study should not be compared to those from the others. The research on caffeine content in espresso coffee indicates the need to report all relevant variables to allow a systematic analysis of the influence of individual parameters while controlling for other factors.