Oxidised Wine: Signs, Causes, and Auction Risk

You cannot taste a wine before you bid on it, and no auction house warrants what is inside the bottle. What you can read is the risk, and it is printed in the lot description if you know which three lines carry it. Oxidised wine is wine that has taken on more oxygen than its sulphur dioxide could absorb, and it fails in a fixed order: colour first, fruit second, then the sherry note that means the bottle is over. The Australian Wine Research Institute (AWRI) describes the ladder running "from a dulling of the aroma, to ‘cardboard’, ‘straw’ and ‘hay-like’ aromas, to ‘sherry-like’ and ‘madeirised’", with "wool’, ‘wet dog’, or ‘varnish-like’" at the far end. We give the visual signal as premature browning or yellowing of the wine. None of that reaches you through a catalogue photograph.

So the question before a sale is not whether the wine is oxidised. It is how the odds stand.

What does oxidised wine smell and taste like?

Tired before it smells like sherry. The AWRI ladder starts with a dulling, and that first rung is the one people talk themselves out of: the wine is not wrong, it is just quieter than it should be, with the fruit sitting behind a layer of straw and cardboard.

On the palate the acid stays and the middle drops out. The AWRI states that acetaldehyde, a compound contributing to oxidation flavour, can impart odours described as "ripe bruised apples’, ‘stuck ferment’ character or ‘sherry’ and ‘nut-like’ characters" at levels above 125 mg/L. Colour moves one way and does not come back: whites deepen to gold and then brown, reds lose the purple rim and go brick then tawny. Our colour and age guide sets out which shade is ordinary at which age.

Two of the AWRI's own descriptors name wines where the oxidation was the intention. The AWRI notes that "for some wine styles, such as sherry, oxidation is deliberately encouraged."

How does ullage predict oxidation risk?

Ullage is the space at the top of the wine bottle not occupied by wine. WineBid states that "A low ullage can indicate seepage and oxidation of the wine, and affect its value considerably." The fill level is a key indicator of a wine's condition and its exposure to oxygen over time.

WineBid names five bands on a Bordeaux-shaped bottle: base of neck or higher, very top shoulder, top shoulder, mid shoulder, and low shoulder. Each band is read against the bottle's age, never on its own. WineBid calls top shoulder "an acceptable and normal fill level for wines 15 years of age and older", and says mid shoulder "may be normal for a wine that is 40 years old or older". A Burgundy bottle has no shoulder to name against, so WineBid states the gap in centimetres between cork and wine and treats two centimetres or less as "an excellent fill for any age". Our ullage levels guide sets those bands against the scales the other houses print.

Which wines oxidise fastest?

Whites go first, and floral whites go fastest. The AWRI states that "White wines made from the ‘floral’ varieties such as Riesling are very prone to oxidation, whereas red wines can withstand significant oxidation during handling due to the higher content of phenolic compounds, which are natural antioxidants."

Phenolics are a buffer a white wine does not have. So two lots at the same fill are not the same risk. Put a Riesling and a Cabernet of the same age side by side, both at mid shoulder, and the AWRI's wording puts the white further along the ladder.

Where does the oxygen actually get in?

Past the cork, not through it. Chanut and colleagues, writing in PNAS Nexus in 2023, tracked the oxygen barrier of the bottleneck and the stopper together for 24 months under conditions simulating wine kept in bottle. The stopper held. They report that the oxygen diffusion coefficient of the stopper alone "is not modified regardless of the storage conditions". The seam between glass and cork is the way in, and at 20°C it carried "nearly 75% of total oxygen transfer" once model wine was present.

Two findings change what you should ask a consignor.

Position is not the tell. Chanut et al. compared bottles stored vertical, cork against the vapour, with bottles stored horizontal, cork against the liquid. Position "does not influence the oxygen transfer". Whether a case sat on its side does not settle the oxygen question.

Heat is the tell, and it runs on a clock. At 35°C the barrier of bottleneck and cork held for 9 months. At 50°C it held for 3. After that Chanut et al. saw the barrier give way, with transfer rising at the glass and cork seam. Their significance statement is blunt: high storage temperature strongly increases oxygen transfer at that interface, while neither temperature nor position touched the intrinsic diffusion property of the microagglomerated corks over 24 months. A lot with a documented storage temperature history tells you more than a photograph of a rack.