South Africa Wine Technical Yearbook 2025

• Notable negative correlations between the OTR T12 and 3MH, 4MMP, dissolved carbon dioxide and total sulphur dioxide, as well as the sensory descriptors described as “Sauvignon blanc character”, which would suggest that the wines showed better preservation and freshness with a higher intensity of typical Sauvignon blanc aromas and descriptors.

These wines had the highest oxidative evolution, the lowest concentration of volatile thiols and FFT, and the highest concentration of oxidation-related compounds. This group also had the lowest dissolved carbon dioxide concentration. The free sulphur dioxide concentration was below 5 mg/L for all the groups.

Results: Sensory evaluation Statistical analysis showed:

• Notable positive correlations between the OTR T12 and the oxidation-related compounds, as well as the sensory descriptor “oxidised”.

Conclusions This stu dy represents one of the first comprehensive analyses of aged closures’ OTRs and their long-term impact on wine quality. The findings provide crucial insights into how closure selection affects Sauvignon blanc’s preservation over time. This study showed that closures with low and stable OTRs (like Saran-Tin-lined screw caps and certain microagglomerated corks) are best suited for retaining desirable Sauvignon blanc characteristics and freshness and maintaining the wine’s aromatic integrity over long-term storage. Wines sealed with higher OTR closures lost these varietal traits and developed oxidation related aromas, diminishing their sensory appeal. While traditional and capable of excellent performance, the natural corks tested in this study show significant variability, making them less predictable over extended

ageing periods. However, it is important to note that some natural corks tested in this study performed just as effectively as the Saran-Tin screw caps. For the specific Sauvignon blanc wines tested in this study, an OTR T12 of below ~ 0.27 mg/year was sufficient to preserve the wines’ signature aromas. In comparison, an OTR T12 of more than ~ 0.82 mg/year posed a risk of noticeable oxidation after 12 years. It should be noted that these concentrations will differ from one wine to the next depending on the capacity of the wine to buffer the effect of oxidation over time. For winemakers, these results highlight the importance of choosing closures with known and reliable long-term oxygen permeability. This understanding allows for better control over the ageing process, particularly for aromatic white wines like Sauvignon blanc, where maintaining freshness and varietal expression is critical. 

For more information, contact Carien Coetzee at carien@basicwine.co.za. Reference https://www.wineland.co.za/otr-and-long-term-ageing-of-sauvignon-blanc-wines/

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TECHNICAL YEARBOOK 2025