Atypical aging and hydric stress: insights on an exceptionally dry year

Abstract

Atypical aging (ATA) is a white wine fault characterized by the appearance of notes of wet rag, acacia blossoms and naphthalene, along with the vanishing of varietal aromas. 2-aminoacetophenone (AAP) – a degradation compound of indole-3-acetic acid (IAA) – is regarded as the main sensorial and chemical marker responsible for this defect. About the origin of ATA, a stress reaction occurring in the vineyard has been looked as the leading cause of this defect. Agronomic, climatic and pedological factors are the main triggers and among them, drought stress seems to play a crucial role.^[1] Available water capacity (AWC) is defined as the amount of water a soil can store that is available for use by plants. AWC might be employed to gauge a predisposition to hydric stress which could ultimately lead to the onset of ATA. Considering previous research which has demonstrated that ATA development is likely to occur in fields having 30-40 mm AWC^[2], this relationship was further investigated in the present study in an exceptionally dry growing season such as 2022.

11 vineyards located in Trento (Italy) were grouped according to their AWC (low, medium, high) and closely monitored over the course of the harvest season.  Given the climate conditions of the year, all of the fields under examination were subjected to drought conditions. While grapevines belonging to the ‘low’ class experienced severe stress conditions (midday leaf water potential, Ψleaf>15 bar), the ‘medium’ and ‘high’ classes were only moderately stressed (15>Ψleaf>12). Accordingly, all wines obtained were affected by ATA, displaying concentrations of AAP above the odor threshold (0.5 μg/L). Nonetheless, the AAP content of the ‘low’ class was significantly higher than the other classes. It was concluded that in exceptionally dry seasons, grapevines planted on fields characterized by a low AWC are more subjected to produce faulty wines characterized by ATA.

Acknowledgements: The authors would like to thank Cavit sc. for the technical and financial support.

References:
1)  Schneider V. (2014) Atypical aging defect: Sensory discrimination, viticultural causes, and enological consequences. Rev. Am. J. Enol. Vitic., 65:277–284, DOI 10.5344/ajev.2014.14014
2) Rauhut D. et al. (2003) Effect on diverse oenological methods to avoid occurrence of atypical aging and related off-flavours in wine. InŒnologie 2003. 7e Symposium International d’Œnology. A. Lonvaud-Funel et al., 376-379