Characterization of intact glycoside aroma precursors of recovered minority Spanish red grape varieties by High-Resolution Mass Spectrometry

Abstract

In Spain, the wide diversity of red grapevine varieties represents an advantage when choosing the most suitable one for cultivation based on different climatic conditions, without implying a loss of their enological potential. In response to this climatic variability, research is focused on adapting minority varieties, which could be more resistant to water and thermal stress, while maintaining the quality and aromatic complexity of the wines. In this context, Tinto Fragoso and Moravia Agria grapevine varieties have attracted the interest of researchers due to their attractive enological properties, according to preliminary studies.

Among the components that define wine quality, the grapes glycosidic aroma compounds have a significant importance. Such compounds are characterized by a structure with two different parts, a sugar moiety, and an active molecule (aglycone), linked by a glycosidic bond. The varietal aroma of wines is mainly due to the glycosidic aroma precursors of grapes, even though such compounds aren’t odorous, the release of their volatile aglycones throughout vinification or wine aging, affect to their aroma and sensory profile. The indirect analysis of this fraction, through determination of the volatile aglycones by hydrolyzing their precursors, may result in chemical artifacts. Additionally, the use of glycosidic enzymes can cause alterations in the sample profile due to their inherent specificity.

The study of the intact glycosidic aroma precursor profile of grape would allow to know the enological potential of recovery varieties. The aim of this work was to study such profile of Moravia Agria and Tinto Fragoso grapes collected from plants cultivated under two water regimes (drought with survival irrigation and deficit irrigation, 20% ETo). The identification and structural characterization of glycosides were performed by high-resolution mass spectrometry using an UHPLC/QTOF analytical system. Compound identification was achieved utilizing a custom-built database (GrapeAroma), and the structures identified were validated through MS/MS fragmentation experiments [1]. The main aroma glycosides detected were pentosyl-hexoside derivatives, with the aglycones of belonging to the chemical classes of benzenoids, aliphatic alcohols, monoterpenols, norisoprenoids, and geranic acid. In general, the two varieties accumulated greater levels of glycosidic aroma precursors under water stress conditions, indicating their adaptability to semi-arid environments.

References

[1] Panighel, A., De Rosso, M., Mazzei, A.R., Fugaro, M., De Marchi, F., Flamini, R. (2024) J Agric Food Chem, 72:4, 1949–1958.