Air temperature

Cool growing conditions favour green aromas in grapes and wines, which can be induced by IBMP (bell pepper nuances) or 1,8-cineole (Table 1). High concentrations of IBMP are not desirable in red wine, but moderate levels of IBMP in Sauvignon blanc are appreciated, because they bring freshness to the wine. Syrah grown in cool climates have higher levels of (-)-rotundone (pepper nuances), which is considered, to a certain extent, as a quality factor. Volatile thiols (in particular 3-SH, grapefruit nuances) are negatively influenced by high temperatures, while Riesling grown in warm conditions contain more TDN (kerosene nuances). Moderately warm conditions favour DMS levels, which are implicated in the complexity of aged wines, while hot conditions trigger cooked fruit aromas, reducing the complexity and ageing potential of red wines.

Radiation (sunlight)

High levels of radiation decrease the concentration of IBMP in grapes and wines, while (-)-rotundone can be enhanced by exposure of the grapes to sun. High radiation has globally a positive effect on wine aromas, in particular on monoterpenes, volatile thiols (3-SH) and TDN. However, excessively high radiation may trigger the presence of ortho aminoacetophenone (AAP, nuances of atypical ageing) in white wine and cooked fruit aromas in red wine, which are putative factors driving premature ageing. In white grapes relying on volatile thiols for their aroma expression (in particular Sauvignon blanc) a side effect of high radiation is an increase in skin phenolics. These may be transformed into quinones during prefermentation operations, which can destroy a part of the precursors of volatile thiols or react with glutathione, a powerful antioxidant compound which has a preserving effect on these aromas.

Nitrogen

Although vine nitrogen status does not have a direct impact on the synthesis of IBMP, unlimited nitrogen uptake may increase vigour and create a cool and shaded microclimate in the bunch zone, indirectly reducing the degradation of green aromas. The synthesis of precursors of volatile thiols is enhanced by nitrogen, as is the production of esters during fermentation, leading to more fruity wines. The production of DMS is triggered by nitrogen, favouring the development of an attractive ageing bouquet. In Riesling, the concentration of TDN and AAP is reduced under increased nitrogen status. A side effect of nitrogen is that it reduces skin phenolics and increases must glutathione, limiting the risk of volatile thiol degradation through quinones. The absence of a limitation in nitrogen supply is globally favourable for aroma expression in wines, but excessive nitrogen should be avoided, because it promotes vigour and may induce Botrytis cinerea infection.

Water

Vine water status is the result of the combined effect of climate (rainfall and reference evapotranspiration), irrigation (if applied) and soil (soil water content). Water deficit is generally favourable for aroma expression in wines, because it reduces green aromas (in particular IBMP) and increases monoterpenes, C₁₃-norisoprenoids and volatile thiols (on the condition that the deficit is moderate). However, it is also known to decrease (-)-rotundone and therefore to affect the peppery typicity. When vines meet water deficit during the berry ripening period, the produced wines develop a more attractive ageing bouquet⁴. Severe water stress, however, promotes atypical ageing related to the development of AAP in Riesling, and may trigger cooked fruit aromas in red wines, probably as an indirect effect of berry shrivel.

Table 1. Effect of four terroir factors (air temperature, radiation, vine nitrogen status, and vine water deficit) on aroma compounds in grapes and wines. References can be found in van Leeuwen et al. (2020)⁵.

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Notes

• van Leeuwen, C., & Seguin, G. (2006). The concept of terroir in viticulture. Journal of Wine Research, 17(1), 1-10. https://doi.org/10.1080/09571260600633135
• van Leeuwen, C., Friant, P., Chone, X., Tregoat, O., Koundouras, S., & Dubourdieu, D. (2004). Influence of climate, soil, and cultivar on terroir. American Journal of Enology and Viticulture, 55(3), 207-217.
• Schmidtke, L. M., Antalick, G., Šuklje, K., Blackman, J. W., Boccard, J., & Deloire, A. (2020). Cultivar, site or harvest date: the gordian knot of wine terroir. Metabolomics, 16(5), 1-17. https://doi.org/10.1007/s11306-020-01673-3
• Picard, M., van Leeuwen, C., Guyon, F., Gaillard, L., de Revel, G., & Marchand, S. (2017). Vine water deficit impacts aging bouquet in fine red Bordeaux wine. Frontiers in Chemistry, 5, 56. https://doi.org/10.3389/fchem.2017.00056
• van Leeuwen, C., Barbe, J. C., Darriet, P., Geffroy, O., Gomès, E., Guillaumie, S., Helwi, P., Laboyrie, J., Lytra, G., Le Menn, N., Marchand, S., Picard., M., Pons., A., Schüttler A. & Thibon, C. (2020). Recent advancements in understanding the terroir effect on aromas in grapes and wines. OENO One, 54(4), 985-1006. https://doi.org/10.20870/oeno-one.2020.54.4.3983