Two dimensions, one mission: unlocking grape composition by GC × GC

Abstract

Aroma is one of the most important attributes that determine consumer’s perception of the sensory quality of wine and varietal typicity. The aroma of grapes consists of big diversity of volatile compounds, including esters, terpenic compounds, C₁₃ norisoprenoids, C₆ compounds, benzene derivatives, alcohols, aldehydes, among others. Given the complexity of the grape volatile profile and the trace concentrations of these compounds, employing advanced analytical techniques such as GC×GC-ToFMS is essential. This method enables efficient separation and precise detection of volatile compounds within the intricate grape matrix [1, 2].

This work aims to analyze the volatile composition of three different Portuguese white grape varieties (Terrantez, Encruzado and Malvasia Fina) using HS-SPME-GC×GC-ToFMS. To increase the efficiency of the SPME technique, a detailed optimization of all the steps of the sample preparation technique was carried out. The optimized conditions were 4 g of grapes, 2 g of NaCl, and 2 mL of H₂O. Additionally, the extraction conditions using a carboxen/divinylbenzene/polydimethylsiloxane fiber were also optimized and performing the extraction for 40 minutes at 60 ºC allow to identify more volatile compounds.

As a result, it was possible to identify sixty free compounds, including four C₆ compounds, three benzenoids, twenty-four monoterpenes, twenty-four sesquiterpenes and five C₁₃ norisoprenoids. The results showed that there are some compounds in only one variety, for example, β-copaene is only present in the Encruzado variety, as well as trans– pyran linalool oxide in the Malvasia Fina variety and, finally, in the Encruzado variety, α-thujone. Compounds such as D-verbenone, δ-elemene, cis-thujopsene, α-muurolene, cubenol, α-cadinene and δ-selinene were only found in the Terrantez and Encruzado varieties, while the compound 5-hexen-2-ol was only found in the Malvasia Fina and Terrantez varieties. Comparing the varieties, Malvasia Fina showed the highest relative total area of C₆ compounds, while Terrantez showed the highest relative total area for benzenoids. In addition, Encruzado revealed the highest relative total area for monoterpenes. Linear discriminant analysis (LDA) further revealed clear differences in the volatile composition between the studied white varieties.

HS-SPME combined with GC×GC-ToFMS provides a suitable and sustainable approach for determining the volatile signature of grapes from different varieties.

Acknowledgement

This research was funded by “Vine&Wine-Driving Sustainable Growth Through Smart Innovation” project (sub-project-BioGrapeSustain), “Mobilizing Agendas for Business Innovation” under the Recovery and Resilience Program. Authors also aknowledges MED https://doi.org/10.54499/UIDB/05183/2020 and CHANGE https://doi.org/10.54499/LA/P/0121/2020.

References

[1] Fonseca, D., Martins, N., Garcia, R., Cabrita, M. J. (2024). Molecules, 29(9), 1989-2005.

[2] Fonseca, D., Martins, N., Garcia, R., Cabrita, M. J. (2025). LWT, 215, 117314-117322.