# Quantitative Analysis of Caffe in Roasted Coffee: A Comparison of Brewing Methods
## 3 Results and Discussion
### Brewing Methods  
Most of the studies included in the review analyzed brewing methods such as Cold Brew (50.0% of the eligible studies), Espresso (40.6%), French Press (28.1%), AeroPress (15.6%), and Moka (15.6%), (Table 4). These studies also analyzed other coffee brewing methods, including American [33; 38; 54], Neapolitan [34; 54], V60 [30; 51; 52; 57], Pure Brew [51; 52], Hot brew [43; 47; 59], Clever [51], Chemex [51]. Overflow methods predominated, with varying brewing parameters and caffeine content obtained. However, the limited number of studies makes it difficult to compare individual parameters and draw conclusions, so the remainder of this article focuses on the five most commonly used coffee brewing methods. Detailed results for each of these methods are presented below. The lack of information regarding the roasting degree and geographical origin of the coffee beans, which varied across studies, made it impossible to determine the impact of these factors on caffeine content accurately. Only 25.0% of the studies included coffee with at least two different roasting levels (light, medium, dark). It is worth noting that there was no standardized classification for roasting levels in the studies, and in some cases, terms such as \"medium light\" or \"medium dark\" were used. Furthermore, while some studies mentioned the roasting degree, they did not correlate this parameter with caffeine content results, nor were appropriate statistical analyses conducted, which further hindered the assessment of its influence on the outcomes. An interesting and clear example is the study by [PERSON] et al. [52], where light-roasted coffee prepared using the French Press method contained higher caffeine content compared to coffee prepared with the AeroPress method. However, for medium and dark-roasted coffee, the results did not show statistically significant differences. Similarly, in the study by [PERSON] et al. [53], espresso made from light and medium-roasted beans had higher caffeine content compared to dark-roasted coffee. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Authors** & **Cold Brew** & **Espresso** & **French Press** & **AeroPress** & **Moka** \\ \hline \(\left[29\right]\) & & & & & \\ \(\left[30\right]\) & & & & & \\ \(\left[31\right]\) & & & & & \\ \(\left[32\right]\) & & & & & \\ \(\left[33\right]\) & & & & & \\ \(\left[34\right]\) & & & & & \\ \(\left[35\right]\) & & & & & \\ \(\left[36\right]\) & & & & & \\ \(\left[37\right]\) & & & & & \\ \(\left[38\right]\) & & & & & \\ \(\left[39\right]\) & & & & & \\ \(\left[40\right]\) & & & & & \\ \(\left[41\right]\) & & & & & \\ \(\left[42\right]\) & & & & & \\ \(\left[43\right]\) & & & & & \\ \(\left[44\right]\) & & & & & \\ \(\left[45\right]\) & & & & & \\ \(\left[46\right]\) & & & & & \\ \(\left[47\right]\) & & & & & \\ \(\left[48\right]\) & & & & & \\ \(\left[49\right]\) & & & & & \\ \(\left[50\right]\) & & & & & \\ \(\left[51\right]\) & & & & & \\ \(\left[52\right]\) & & & & & \\ \(\left[53\right]\) & & & & & \\ \(\left[54\right]\) & & & & & \\ \(\left[55\right]\) & & & & & \\ \(\left[56\right]\) & & & & & \\ \(\left[57\right]\) & & & & & \\ \(\left[58\right]\) & & & & & \\ \(\left[59\right]\) & & & & & \\ \(\left[60\right]\) & & & & & & \\ \hline \hline \end{tabular} Abbreviations: \(\bullet\)—denotes the specific brewing methods applied in this study.  
\end{table} 
Table 4: Articles included in the review with consideration of the coffee brewing methods used. Regarding geographical origin, according to the data presented in Table 1, only some of the study materials came from the same region, but other parameters, such as roasting degree and brewing method, differed across studies. For this reason, it is not possible to conclusively attribute caffeine content to a specific geographical location. To accurately assess the impact of geographical origin on caffeine content, all variables that may influence the results, such as coffee species, roasting degree, and brewing method, must be considered.