How to Decant Wine: When to Aerate and Remove Sediment

How to decant wine comes down to two purposes. You can decant to expose the wine to oxygen, thereby releasing aromatic molecules. You can also decant to separate it from solids like dead yeast, lees, or tartrate crystals. A decanter is a packaging accessory that can facilitate this process. Exposing wine to oxygen can enhance its bouquet. The oxygen releases aromatic etheric, ester, and aldehyde molecules. This practice can be particularly beneficial for wines that need to "open up" their aromas. Furthermore, winemaking processes sometimes result in the presence of solids. Aging separates wine from dead yeast and other solids, called lees. It also describes tartrate crystals, which tartaric acid and potassium form, as looking like "grains of clear sand" or "wine diamonds." While harmless, they can appear as sediment. Decanting allows you to leave these solids behind, ensuring a clear presentation.

Why should you decant wine?

Decanting wine serves two primary purposes: to introduce oxygen and to separate unwanted solids. Gently swirling the wine in a wine glass best reveals its bouquet. The swirl exposes the wine to more oxygen, which releases aromatic etheric, ester, and aldehyde molecules. This principle extends to decanting. A larger surface area of wine meets air, potentially enhancing the wine's aromatic profile. This can be particularly useful for younger wines, allowing them to express their full range of aromas more readily.

Beyond aromatic development, decanting addresses the presence of various solids that can form in wine. During the winemaking process, wine is separated from "dead yeast and any solids that remained (called lees" and transferred to a new container. These lees can be present even in finished wines. Tartrate crystals, formed by tartaric acid and potassium, which appear are "wine crystals" or "wine diamonds." While these are harmless, they can be visually unappealing to consumers. Decanting provides a method to separate the clear wine from these precipitates.

Additionally, aeration can address certain reductive wine faults. The Australian Wine Research Institute (AWRI) identifies hydrogen sulfide (H2S), known as rotten egg gas, as a volatile sulfur compound that forms in wine. The AWRI states that Aeration might also oxidise H2S to elemental sulfur (S), which, if removed, prevents it from reforming H2S. This suggests that introducing oxygen can help mitigate some unpleasant reductive aromas.

When should you decant wine?

The decision to decant often depends on the wine's age and its specific characteristics or potential faults. For younger wines, decanting can help "open up" their aromas by exposing them to oxygen. This allows the wine's aromatic compounds to develop and become more expressive before consumption.

For older wines, decanting is primarily useful for separating sediment that has accumulated over time. Wine can age for "over twenty years for wine of good structure with high levels of acid, tannin or sugar." During this extended aging, natural precipitates like tartrate crystals or residual lees can form. Removing these solids ensures a clear pour and a more pleasant drinking experience. You can assess the maturity of your holdings and determine optimal drinking windows. Consult resources like decant times by maturity of the wines we track.

However, decanting is not universally beneficial. It can do harm to certain wines, or where specific faults are present. Sometimes a wine already exhibits signs of oxidation, such as 'cardboard', 'straw', 'hay-like', or 'sherry-like' aromas, as described by the AWRI. Further exposure to oxygen through decanting would likely worsen these characteristics. The AWRI notes that oxidation faults are "much less common today with the application of refrigeration, inert gas blanketing during the production and packaging operations and effective sulfur dioxide management," but they can still occur.

Decanting also does not resolve all wine faults. The AWRI states that 2,4,6-trichloroanisole (TCA), the main compound responsible for cork taint with its "musty, mouldy aroma," is "one of the most odour intense compounds known." There is no indication that decanting can remove this taint. Similarly, the AWRI notes that "mousy taint,"an off-flavour reminiscent of caged mice or"rarely detected by sniffing because the compounds involved are not volatile at wine pH" and "There is no satisfactory method to remove mousy off-flavour."

Consider the overall condition of your wines, including fill levels, which can indicate potential for oxidation. You can learn more about this in our guide on wine ullage levels explained.

What are common wine solids and how do they form?

Wine can develop various solids during its production and aging, which decanting can help to separate. One common type of solid is known as lees. After primary fermentation, and after a period in which the wine stands or ages, the wine is separated from the dead yeast and any solids that remained (called lees. These lees are a natural byproduct of fermentation. They can consist of spent yeast cells and other fine particles from the grapes. While often removed during winemaking through processes like racking, some fine lees may remain and settle out over time in the bottle.

Another type of solid you might encounter in wine are tartrate crystals. We describe "cold stabilization"a process used in winemaking to reduce tartrate crystals (generally potassiumgenerally potassium bitartrate. The union of tartaric acid, a natural acid in grapes, and potassium forms these crystals. They look like grains of clear sand and are also known as "wine crystals" or "wine diamonds." While they are harmless and do not affect the wine's flavor, they can appear as sediment in the bottle, particularly if the wine has been stored under cold conditions. Consumers can sometimes mistake them for glass shards or wine faults. Decanting allows for the separation of these crystals, improving the wine's aesthetic clarity.

How does decanting affect wine faults?

Decanting, through aeration, can have a specific impact on certain wine faults, particularly those related to reduction. The AWRI identifies several reductive wine faults caused by volatile sulfur compounds. One is hydrogen sulfide (H2S), which has an aroma of rotten egg gas. The AWRI states that Aeration might also oxidise H2S to elemental sulfur (S), and that this sulfur precipitate "must be removed" to prevent it from reforming H2S. This suggests that carefully introducing oxygen can help to dissipate hydrogen sulfide.

However, the effect of aeration on other reductive compounds can be more complex. The AWRI notes that sulfhydryls, also known as 'thiols' or 'mercaptans', have aromas described as 'cabbage', 'garlic', 'onion', and 'rubber'. If a wine containing methanethiol and ethanethiol (types of mercaptans) "is aerated to remove a suspected hydrogen sulfide fault, these can be oxidised to DMDS and DEDS, which do." The AWRI specifies that DEDS and DMDS "do not react with copper and therefore cannot be removed by copper fining." This indicates that while aeration might address H2S, it can convert mercaptans into disulfides, which are more difficult to remove.

For other wine faults, decanting offers no known remedy. The AWRI states that 2,4,6-trichloroanisole (TCA), the compound responsible for cork taint, imparts a "distinct musty, mouldy aroma" and is "one of the most odour intense compounds known." The AWRI found that TCA at a concentration as low as 1 ng/L suppressed the ratings for overall aroma intensity and for positive fruit-derived characters of a Semillon wine during sensory evaluation. Similarly, the AWRI states that there is no satisfactory method to remove mousy off-flavour, and reports that some wines develop mousy taint when exposed to air or oxygen.

Decanting is also inappropriate for wines already suffering from oxidation faults. The AWRI lists oxidation characteristics ranging from a "dulling of the aroma" to 'cardboard', 'straw', 'hay-like', 'sherry-like', and 'madeirised' aromas. Introducing more oxygen to an oxidized wine would exacerbate these undesirable characteristics. Understanding the potential impact of aeration on various faults is crucial for collectors managing their fine wine investment.

How does serving temperature relate to decanting?

Decanting focuses on aeration and sediment removal. Serving temperature also plays a significant role in a wine's sensory perception. It works in conjunction with decanting, or independently of it, to optimize enjoyment. "The temperature that a wine is served at can greatly affect the way it tastes and smells." Specifically, "Lower temperatures emphasize acidity and tannins while muting the aromatics," whereas "Higher temperatures minimize acidity and tannins while increasing the aromatics." This highlights how temperature directly influences the expression of a wine's bouquet, much like aeration.

The International Organisation of Vine and Wine (OIV) provides recommended serving temperatures for various wine categories in its standard for international wine competitions. These guidelines set conditions that let each wine show its characteristics at their best. The OIV emphasizes that "It is essential that all products of the same type within the same session, shall be tasted at the same temperature."

Here are the OIV's recommended serving temperatures:

Wine Type	Temperature (°C)
White and Rosé wines	10-12
Red wines	15-18
Sparkling wines	8-10
Naturally sweet wine, ice wine, liqueur wine and mistelles	10-14
Spirituous beverages of vitivinicultural origin	12-16

Considering both decanting and precise temperature control allows you to present your wines optimally. For instance, a young, full-bodied red wine might benefit from decanting to enhance aromatics. Serving it at 15-18 °C further increases those aromatics. Conversely, you should leave a delicate sparkling wine undecanted, served at 8-10 °C as per OIV recommendations. "Sparkling wine should not be swirled to the point of releasing bubbles," implying that excessive aeration is undesirable.

Understanding these nuances helps you make informed decisions for each bottle, whether it's a Bordeaux you've held for decades or a recent acquisition.

Maximize the enjoyment of your collection by understanding the optimal drinking windows for each bottle. Our drink-window model provides precise guidance on when your wines are at their peak. It helps you decide whether to open, hold, or consider selling.