## 4 Conclusions  
The HS-SPME/GC \(\times\) GC-ToFMS analysis allowed the detailed characterization of single-dose capsule coffee-based blends, relating the volatile composition of coffee powders with the respective expressos brews. This high throughput methodology allowed the detection of a wide number of volatiles (a total of 390 volatile compounds, considering both samples from 8 single-dose commercial coffee capsules), belonging to 17 chemical families. From these, 100 volatile compounds (ca. 26%) were determined for the first time in roasted coffee or coffee brews. The use of 2D-GC allowed defining a volatile compounds' profile for each blend, enabling the comparison of blends in respect to the compounds present in trace amounts that could predict coffee brew aroma when analyzing the volatile compounds of the respective coffee powder. The different volatile profile of the powder and the brew from the same capsule blend suggests that both matrices should be considered when defining coffee blend characteristics and potential consumer acceptance. However, the selection of highly correlated compounds between the two matrices can be used to predict the volatile potential of an espresso brew when analyzing the coffee powder. **Supplementary Materials:** The following are available online at [[https://www.mdpi.com/article/10.3390/foods10102508/s1](https://www.mdpi.com/article/10.3390/foods10102508/s1)]([https://www.mdpi.com/article/10.3390/foods10102508/s1](https://www.mdpi.com/article/10.3390/foods10102508/s1)), Figure S1: Blow-up of the GC \(\times\) GC-ToFMS chromatograms contour plot obtained in full-scan acquisition mode for the 8 capsule coffee powders (left) and respective espresso brews (right) under study, Figure S2: Mean values of GC \(\times\) GC peak areas for the compounds analyzed (ordered by chemical family as in Table 1 and Table S1) and corresponding relative standard deviation (RSD) among all samples (8 blends), Figure S3: GC \(\times\) GC peak areas for the different chemical families determined in the coffee brews considering the blends labeled with different intensities: Blend 1 (intensity 5); Blend 2 (intensity 9), and Blend 3 (intensity 10), Figure S4: Representation of the correlation between coffee powder and coffee brew GC \(\times\) GC peak areas of the 390 compounds putatively identified through Pearson's correlation coefficients and p-values associated. Column 1 shows the correlation coefficients of each compound, grouped by its chemical family, illustrated through a chromatic scale shown in column 2, from dark blue (r low values), to dark red (r high values). Column 3 shows the \(p\)-values of each compound, grouped by its chemical family, illustrated through a chromatic scale shown in column 4, from light green (\(p\) low values), to dark green (\(p\) high values), Table S1: Chromatographic details and aroma descriptors of 390 volatile compounds putatively identified in 8 capsule-coffee powders and espresso brews using HS-SPME/GC \(\times\) GC-ToFMS, Table S2: GC \(\times\) GC peak areas of 390 volatile compounds putatively identified in 8 roasted ground capsule-coffee powders and respective espresso brews, using HS-SPME/GC \(\times\) GC-ToFMS. **Author Contributions:** Conceptualization, M.A.C. ; methodology, M.P. and A.S.F. ; validation, S.P. and G.R.L. ; formal analysis, S.P., G.R.L., M.P. and A.S.F. ; investigation, S.P. and G.R.L. ; resources, M.A.C. ; data curation, S.P., G.R.L., C.P.P. and E.C. ; writing--original draft preparation, S.P. and G.R.L. ; writing--review and editing, M.A.C., S.M.R., E.C., C.P.P., C.F., C.R., G.R.L. and S.P. ; visualization, M.A.C., S.P. and G.R.L. ; supervision, M.A.C. and S.M.R. ; project administration, M.A.C. ; funding acquisition, M.A.C., C.F. and C.R. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by Novadelta, S.A., through a QREN individual I&DT project, CoffeeArt FCOMP-01-0202-FEDER-024886, Portugal.