South Africa Wine Technical Yearbook 2025

AUGUST

SHUTTERSTOCK

OTR and long-term ageing of Sauvignon blanc wines By Carien Coetzee

Introduction The OTR of wine bottle closures refers to the amount of oxygen that passes through the closure into the wine over time. This rate is critical because excessive oxygen exposure can lead to undesirable effects, including loss of vibrant fruit flavours, browning of the wine, and the development of oxidised aromas. Different closures have varying OTRs, affecting how the wine evolves in the bottle. Past studies investigated the OTR of bottle closures during the initial stages after bottling, while the stopper is freshly inserted and therefore still “new”. Little data exists regarding the OTR over an extended period and the potential changes in oxygen transfer that may occur over longer storage durations.

Abstract A study on the oxygen transfer rate (OTR) of wine closures and its impact on Sauvignon blanc ageing over 12 years revealed that closures with lower and stable OTRs best preserved the wine’s fresh aromas and varietal character. In contrast, closures with higher OTRs led to increased oxidation and diminished sensory appeal. Natural corks exhibited high variability, making their long-term performance less predictable, though some performed as well as Saran-Tin lined screw caps. These findings emphasise the importance of selecting closures with controlled and consistent oxygen permeability to maintain the integrity of aromatic white wines over extended storage.

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TECHNICAL YEARBOOK 2025