Modelling colour stability and ageing potential in SA red wines

Project Number
WW WdT 17-01

Project title
Modelling colour stability and ageing potential in SA red wines

Project leader
du Toit, W

Institution
Stellenbosch University: Department of Viticulture and Oenology

Team members
Mihnea, M
Aleixandre Tudo, J L

Project description
The main objective of this project was to follow the phenolic evolution of a large number of red wines and to predict and corroborate their ageing capacity.

Methods
A wide range of phenolic analyses (spectrophotometric and HPLC) were employed as well as sensory assessments by winemakers on a range of red wines. Advanced statistical analyses were employed to analyse the large datasets generated. We also assessed winemakers’ prediction of certain red wines’ ageing capacity and confirmed how well these wines aged after a period of time.

Key Results
Evolutions of phenolic compounds were seen in both commercial and experimental wines. Winemakers rated wines with a relative low or high ageing potential correctly, which was confirmed after three years of ageing, but in a large number of wines they did not agree on this. The phenolic analyses performed could not explain the sensorial results obtained, but we were able to develop a phenolic concentration and evolution ageing index.

Key Conclusion of Discussion
Wines with a very low or high ageing capacity can be sensorially predicted by winemakers to age accordingly. However, factors other than only phenolics probably also play a role in the ageing capacity of wines, which might also explain the variation seen between winemakers’ ability to predict the ageing ability of most other red wines tested. However, the phenolic evolution of most commercial red wines seems to follow a certain pattern. An aging index based on phenolic concentration and evolution (stability) only was obtained. This aging index correlates well with some of the most relevant phenolic measurements. Wines with high phenolic based aging index values are generally wines with initial high levels of tannins, anthocyanins, flavonols and therefore phenols and polymeric pigments. The index provides values in the range of 0 to 7.5. Values of the index were obtained for low aging potential wines (0-2,5), medium (2.5- 4,5) and high (4,5- 7.5). However, this phenolic aging index values could not be correlated with the sensory scores provided by the winemakers. Factors other than only phenolics probably also played a role in the winemakers’ ability to predict the ageing ability of most of the red wines tested.

Take Home message for Industry
Wines with increased mouthfeel and persistence seem to age better, but not only phenolic analyses should be kept in mind when assessing a wine’s ageing capacity. However, high or low phenolic wines should still have a similar phenolic profile after ageing. By using the proposed phenolic ageing index, wine producers might be able to better understand how their wines’ phenolic profiles might look like after an ageing period of 12 to 36 months. General ageing capacity of the wine should, however, be complimented with sound sensorial analyses as well.

Publications

Jose Luis Aleixandre-Tudo , Wessel du Toit. 2020. A chemometric approach to the evaluation of the ageing ability of red wines. Chemometrics and intelligent laboratory systems, 104067, 1-9. https://doi.org/10.1016/j.chemolab.2020.104067

J. L. Aleixandre-Tudo, W. J. du Toit. 2020. Evolution of phenolic composition during barrel and bottle aging. South African Journal of Enology and Viticulture Vol 41 (2). https://doi.org/10.21548/41-2-4128

 

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