## 3 Results and Discussion
### Sensory Analysis  
The SCA (Specialty Coffee Association) protocol is designed for quality assessment, and finding significant differences is complex because the protocol is based on a specific description of sensory attributes [37]. Aroma, flavor, aftertaste, acidity, body, balance, and an overall score were the evaluated parameters. Sensorial analysis results are represented in a spider graph in Figure 3A, while the adopted quality scale and the values can be consulted in Tables 1 and 3. A statistically significant difference was reported for all the analyzed parameters between the four groups of samples except for acidity. In general, PB filter coffees were valued with the highest scores of aroma, body, balance, acidity, and overall impression, while FP reported the lowest scores of all the investigated aspects except for acidity, which was similar to the others. The chosen specialty coffee from Kenya is well-known for its flavor, complexity, and acidity notes. Coffee cup acidity derives from several factors, not only the extraction method. In this study, this parameter was evaluated through a sensorial analysis to compare the beverages from different extraction methods, reporting all similar (no statistically significant differences) and elevated scores due to this intrinsic characteristic of coffee. Figure 2: Heatmap of VOCs analyzed by hierarchical clustering. Each row represents a single compound, which is colored according to the chemical class. Each column represents an individual filter coffee sample. Cluster analysis was performed using Ward method. Red indicates a high content, and blue indicates a low content of each VOC. Figure 3: Sensorial analysis results of the four filter coffee comparisons. (**A**) Spider gram with the attributed values. Statistically different values according to ANOVA results are reported with an asterisk. (**B**) Feature view plots of the three main sensorial parameters related to coffee volatile profile extracted from the ANOVA loadings plot. A consistent sense of sweetness and roundness was observed in the PB samples, with a smoother and fuller acidity; the acidity ranged from 7.50 to 7.75 (the highest acidity score). In addition, the aftertaste was smoother and less sweet than the other extraction methods used for this analysis (average value of 7.46). For V60, however, acidity predominated (the average acidity score was 7.75); in this case, roundness was lacking (probably due to the use of the paper filter). This lack of roundness could be related to the high presence of pyrazines in this system, such as 2-ethyl-3-methylpyrazine, 2,3-dimethylpyrazine, and 2-ethyl-6-methylpyrazine, which are associated with earthiness and mustiness in the literature. Meanwhile, AeroPress extractions gave a flat result in the cup, with little body and excess coffee grounds in the middle of the results, despite the higher presence of molecules associated with positive notes, such as the class of terpene alcohols. Given the concentrations and the method of extraction, the final result was a watery cup of coffee. Finally, the French press cups, on average, gave a higher result than the AeroPress cups. In summary, the differences between the extraction methods resulted in diverse cups (one more watery, one sweeter, and another more intense). The result that unites the Pure Brew and French Press systems is related to the presence of two aldehydes most detected in both systems: 2-methylbutanal and 3-methylbutanal, which are associated with fruity and nutty flavors, and both share the metal filter. In conclusion, from the sensorial analysis, Pure Brew resulted in the most performing extraction system as it was assigned the highest score in terms of overall 7.75 and also resulted in the most balanced, acidic, aromatic, and pleasant cup of filter coffee among the analyzed. Figure 3B reports the feature view plots of the three main sensorial parameters related to the coffee volatile profile extracted from the ANOVA loadings plot.