Triterpenoids from Quercus petraea: Identification in Wines and Spirits and Sensory Assessment

Abstract

Eight new triterpenoids (1–8), the known genin (9), and two known functionalized triterpenoids (10 and 11) were isolated from a Quercus petraea heartwood extract. The structures of the new compounds were unequivocally elucidated using HRESIMS and 1D/2D NMR experiments. Sensory analyses were performed in a non-oaked wine on the pure compounds 1–11. Except compounds 1 and 11, all molecules exhibited a sweet taste at 5 mg/L that was particularly intense for compounds 3 and 9. Using LC-HRMS, compounds 1–11 were observed in an oak wood extract and in oaked red wine and cognac. They were also semiquantified in several samples of sessile (Q. petraea) and pedunculate (Q. robur) oak wood extract. All compounds were found in quantities significantly higher in sessile than in pedunculate oak wood. These results support the hypothesis of their contribution to the increase in sweetness during oak aging and show that they can be used as chemical markers to identify the species of oak used for cooperage.

Untargeted UHPLC‐Q‐TOF‐HRMS based determination of discrimating compounds for oak species Quercus robur L. and Quercus petraea Liebl. identification

“…6,7 Lastly, elution of less polar terpenic compounds such as quercotriterpenosid or bartogenic acid was observed after 8 min. [8][9][10] These later eluted compounds seem to induce the main chromatographic differences between sessile and pedunculate oak extracts and indicate the presence of species markers in this area of the chromatogram.…”

“…For coopers, a molecular determination of woods and its impact on wine ageing would allow a better prediction and optimisation of the sensorial quality of casks. Indeed, oak used for wine ageing modifies the sensorial characteristics of wine by releasing various wood compounds (aromatic compounds, 1,2 tannins, 3–5 bitter 6,7 and sweet 8,9 taste compounds) into the beverage 10,11 and by the slow oxygenation process occurring during ageing 12–14 . The selection of the wood to be used in the production of the staves plays an essential role in determining the quality of a barrel; coopers therefore pay great attention to their supplies of oak 15–17 …”

Oak Species Quercus robur L. and Quercus petraea Liebl. Identification Based on UHPLC-HRMS/MS Molecular Networks

“…Cluster 9, also composed of molecules belonging to the triterpenoid family, is specific of sessile oaks with glycosylated terpenoids such as quercotriterpenoids [11,13]. Currently, around ten quercotriterpenoids have been identified.…”

“…Oak barrels are not just containers used for transport but have become an essential tool for aging wines and spirits. The oak used for wine aging modifies the sensory characteristics of wine by releasing various wood compounds, such as aromatic compounds [2][3][4][5], tannins [6][7][8], bitter [9,10], and sweet [11][12][13] tasting compounds into the beverage and by the slow oxygenation process occurring during aging [14][15][16]. The differentiation of species was initially based on tannin content or on the analysis of volatile compounds.…”

Understanding sweetness of dry wines: First evidence of astilbin isomers in red wines and quantitation in a one-century range of vintages

“…In dry wines, sweetness does not result from the presence of residual sugars as in sweet wines, but is due to other non-volatile compounds. Natural sweet compounds released by oak wood [2,3] or yeast lees [4] have been identified by taste-guided purification. Recently, such an approach allowed the isolation of two compounds from grapes that might contribute to the sweetness of dry wines: epi-DPA-G and astilbin [5,6].…”