Sauternes Colour: What it Means for Aged Wines

Sauternes colour is only one clue to a mature bottle. Assessing the condition of aged wines matters, particularly for bottles acquired at auction. You need to understand the factors that influence their longevity and potential for spoilage. The fill level, or ullage, of a wine bottle provides insight into its storage history and potential exposure to oxygen. That exposure can lead to oxidation-type faults and affect a wine's overall visual characteristics. WineBid inspectors are trained to document every possible bottle detail, including ullage. It can affect a wine's value considerably. A lower fill level suggests air has seeped into the bottle, causing the wine to oxidise. That is according to Matt Walls, DWWA regional chair for Rhône, speaking to Decanter.com in 2018. This oxidation can lead to a dulling of the aroma. It can also bring 'cardboard', 'straw', 'hay-like', 'sherry-like', or 'madeirised' sensory characteristics, as noted by the Australian Wine Research Institute (AWRI).

What is ullage and why is it important for aged wines?

Ullage, also known as the fill level or headspace, is the space between the wine and the top of its container. That container may be a barrel or a bottle. This headspace is primarily a mixture of alcohol and water vapors with carbon dioxide, a by-product of fermentation. In containers that are not completely air-tight, such as cork-stoppered wine bottles, oxygen can also seep into this space. While some oxygen is beneficial to the aging process, excessive amounts can lead to oxidation and other wine faults. Decanter states that producers aim for fill levels of 3-10mm at the time of bottling. Over time, some wine will be lost through cork absorption and evaporation. The ullage level in a bottle is an important indicator of the care and storage conditions a wine has received. Auction houses and retailers of mature wines pay close attention to ullage levels when determining a wine's resale value. David Dudley-Jones of Dudley Jones Fine Wines spoke to Decanter magazine in 2016. Lower fill levels and resultant seepage usually point to heat exposure and poor storage, he stated. WineBid considers anything in the neck of a Bordeaux bottle or similar a perfect fill level. That holds for any bottle of any age. A very top shoulder fill is excellent for any wine more than 20 years old. For Burgundy bottles, WineBid states a separate rule. Two centimeters or less between the cork and wine is an excellent fill for any age. For a comprehensive guide to understanding fill levels, refer to our wine ullage levels explained resource.

How do storage conditions affect wine aging and ullage?

Storage conditions significantly influence the rate of evaporation, oxygen ingress, and ultimately, a wine's aging trajectory. Long-term storage requires a temperature of around 13°-15°C and a humidity level of 70% or so. It also requires an absence of light and vibration, according to Dirceu Vianna Junior MW, quoted in Decanter. Wines kept at ambient humidity levels and in temperatures between 10-15°C fare better. They experience evaporation and diffusion at a slower rate than wine kept in lesser conditions. They will thus have lower ullage levels. The natural process of evaporation creates ullage in barrels by causing alcohol and water particles to escape as vapors. This loss is sometimes referred to as the 'angel's share'. A wine stored on its side stays in contact with the cork. Some wine will then be lost by absorption into the cork. Longer corks potentially absorb more wine than shorter corks.

Research by Chanut et al. in 2023 investigated the evolution of oxygen barrier properties of microagglomerated cork-based stoppers over 24 months. The work mimicked various wine conservation conditions using model wine. Their study found that the oxygen diffusion coefficient of the cork stopper alone was not modified. That held regardless of storage conditions such as temperature, storage position, or the presence of model wine. However, the total oxygen transfer includes transfer through the stopper and at the glass-cork interface. The presence of model wine modified it, increasing the value from 2.3 x 10^-11 to 4.7 x 10^-11 m^2 s^-1 after the initial three months of storage at 20°C, according to Chanut et al. This increase means the transfer at the glass-cork interface accounts for nearly 70% of the total oxygen transfer, Chanut et al. reported.

The storage position of the bottle can be vertical (cork in contact with vapor) or horizontal (cork in contact with liquid). Neither position significantly influenced oxygen transfer through the bottleneck-cork system in the Chanut et al. study. However, temperature had a strong impact on oxygen transfer. At 20°C, oxygen barrier properties remained unchanged over 24 months. At 35°C, a temperature easily reached during bottle shipping, a significant transfer at the glass-cork interface started to occur beyond nine months of storage, Chanut et al. found. At 50°C, this shift occurred within the first three months of storage. The value then approached the diffusion coefficient of oxygen in the air, indicating leakage at the glass-cork interface, Chanut et al. concluded. This could be due to a partial melting of the surface treatment agent on the cork. That agent is composed of paraffin and silicon. Another possible cause is a modification of the stopper's mechanical properties, Chanut et al. suggested. For instance, at 50°C, the liquid:solid ratio of the coated product was estimated at 41%, compared to 6% at 20°C, as per Chanut et al. To ensure optimal conditions for your collection, explore our guides on how to store wine.

What are the signs of oxidation in aged wines?

Oxidation can manifest in various sensory characteristics, often indicating spoilage rather than desirable aging. The Australian Wine Research Institute (AWRI) describes oxidation-type faults as ranging from a dulling of the aroma to 'cardboard', 'straw', and 'hay-like' aromas, to 'sherry-like' and 'madeirised'. In extreme cases, a 'wet wool', 'wet dog', or 'varnish-like' aroma can be evident, according to AWRI. Acetaldehyde has a sensory threshold of 100-125 mg/L. It can impart odours described as 'over-ripe bruised apples', 'stuck ferment' character, or 'sherry' and 'nut-like' characters if levels exceed 125 mg/L, AWRI states. Acetaldehyde levels increase as wines age due to chemical oxidation of ethanol, AWRI notes.

Volatile acidity (VA), often perceived as the odour of vinegar, is another indicator of spoilage. The aroma threshold for acetic acid, the major component of VA, is as low as 0.1-0.125 g/L. It is usually considered detrimental above 0.7 g/L, according to AWRI. Increased levels of acetic acid in stored wines are typically due to the growth of acetic acid bacteria. These bacteria convert alcohol to acetic acid in the presence of oxygen, AWRI explains. Ethyl acetate is perceived as the odour of nail polish remover, with a sensory threshold of 12 mg/L. It can also contribute to the sensory perception of volatile acidity, AWRI reports. While low levels (30-60 mg/L) can add 'fruity' aroma properties, concentrations around 150-200 mg/L indicate defective wines, AWRI states.

It is important to note that while some oxygen is beneficial, excessive amounts can lead to these faults. Vintage Port might be slightly less prone to damage since it is fortified. Madeira wines are the only ones that cannot be damaged by oxidation, because they are already oxidized. Therefore, for most wines, managing oxygen exposure through proper storage and closure integrity is vital for preserving quality.

How do auction houses assess bottle condition?

Auction houses and wine merchants employ specific terminology and inspection practices to assess the condition of older vintages. Ullage is a primary focus. WineBid inspectors are trained to document every possible bottle detail. That covers label, capsule, and cork condition issues, as well as provenance, according to WineBid. Provenance is the ownership history of a wine. It is particularly important for establishing the estimated value of very old, rare, or valuable wines, WineBid states. If provenance is unknown, WineBid either rejects the wines or states it clearly on lot descriptions. For more on navigating the market, see our guide on how to sell fine wine.

Michael Broadbent is a Master of Wine and senior consultant of Christie's auction. He developed a guide for evaluating ullage levels of matured wines in the late 1980s. The wine market has used it widely. The terms used to describe fill levels differ for Bordeaux and Burgundy wines due to their distinct bottle shapes, Decanter confirm.

Here is a comparison of ullage terms for Bordeaux and Burgundy bottles:

Ullage Description (Bordeaux)	WineBid Assessment	Decanter/Christie's Assessment	Broadbent's Ullage Guide
Base of neck or higher	Perfect fill for any age		0.12 in (0.3 cm): Normal for young wines; 0.2 in (0.5 cm): Good for any age
Very top shoulder	Excellent for >20 years old
Top shoulder	Acceptable/normal for >15 years old; Very good for >35 years old	Normal for any claret 15 years or older	0.6 in (1.5 cm): Normal for older wines; Good for >15 years
Mid shoulder	Normal for >40 years old	Not abnormal for 30-40-year-old wine	1.18-1.38 in (3-3.5 cm): Mid to mid-low shoulders; Possible oxidation; Price should reflect risk
Low shoulder	Occurs in older wines	Risky, usually only accepted if wine or label exceptionally rare or interesting	2.36-2.75 in (6-7 cm): Extremely risky; Possibly undrinkable

Ullage Description (Burgundy)	WineBid Assessment	Decanter/Christie's Assessment
Two centimeters or less	Excellent fill for any age
Three centimeters	Perfectly normal for >12 years old; Excellent for >25 years old
Four centimeters	Normal for >20 years old; Excellent for >35 years old
Five centimeters	Not uncommon in >30 years old wines
Up to 7cm		Relatively normal in 30-year-old Burgundy

Matt Walls advised in Decanter that if the fill level is much below the bottom of the neck of a Bordeaux bottle, you should think twice before buying it. He also noted that Burgundy bottles are harder to gauge due to their tapering shape. While ullage is a strong indicator, it is not foolproof. Some old bottles with low fills can remain in good condition, Walls stated in Decanter. Dirceu Vianna Junior MW recommends establishing the provenance of the bottle to minimize risks, according to Decanter. Other checks include shining a strong light at the punt to look for sediment and abnormal loss of colour. You can also cut the capsule to inspect the cork for seepage. Another option is to gently touch the cork to ensure it does not move, Decanter suggests. These insights are vital when you buy wine at auction.

To make informed decisions about when to open or hold your fine wines, leverage our comprehensive vintage maturity charts. For a deeper dive into specific vintage performance, you can explore our Château d'Yquem decade by decade against our Sauternes vintage maturity data.