With this process, which can be practiced optionally before drinking wine, the opinions of experts are diametrically opposed. In principle, there are three different directions: 1. wine must be decanted because it must "breathe", i.e. come into contact with oxygen, in order to develop the aromas optimally. 2. According to scientific findings, decanting has no effect at all and is therefore of no importance. 3. Decanting a wine is even harmful and damages its quality. So what is objectively correct? The only thing that is clear is that even recognised experts have divergent opinions. The famous French oenologist Émile Peynaud (1912-2004), one of the most important wine tasters and scientists in this field, is a clear opponent of decantation and said If decanting is necessary at all, it should be done at the latest possible moment, immediately before drinking the wine.
Peynaud even believes that the influence of oxygen has a fundamentally negative effect, causing a diffuse aroma of the wine and the flavours to dissipate. With the majority of wines, decanting does not help at all. After countless personal experiments with various wines, Peynaud summarises as follows: Old wines lose their bouquet more or less quickly and die in the carafe. High quality wines with long barrel storage and varietal wines lose bouquet, body and personality when decanted several hours before drinking. In contrast, decanting can be beneficial for wines with olfactory defects or foreign tastes
The oenologist Michael Broadbent (1927-2020) also believes that aeration is only useful for young wines (red wines), for older wines less so and for old wines not at all. Particularly old wines that are not outstanding in terms of quality and have less character are at risk, because they can decompose and turn into vinegar within a short time (hours to minutes) through contact with oxygen. He does not see this as extreme as Peynaud, but ascribes relatively little effect to decanting. At best, the wines become somewhat softer (which can also be a disadvantage). The famous wine author Hugh Johnson says that decanting definitely changes a wine. In his opinion, whether to the advantage or disadvantage depends on the wine and personal taste.
In the USA, scientific research has shown that decanting has no demonstrable influence on the wine, because enrichment with oxygen takes place - if at all - only on the surface. It is often cited as "proof" that a wine that has been under the "influence of oxygen" for a long time differs from a wine that is enjoyed immediately after opening. For example by "a fruitier and milder taste". But even this does not bring clarity, because it may be related to the fact that the palate, e.g. after the first sip of a tannic wine, has meanwhile got used to the astringency and the wine only apparently tastes different. Even dishes that have been enjoyed in the meantime or a different wine temperature have an influence and can cause different sensory impressions.
A special decantation method called "slow oxygenation" (slow oxygenation method) is mainly used for old red wines, but the famous French wine collector François Audouze also propagates others. First of all, the bottle is closed and left standing upright two days before the planned enjoyment. Then it is uncorked and left without decanting, with the cork only placed on the opening to protect it from dust or insects. Audouze recommends four to five hours for very old wines (30 to 40 years and older) and five to ten hours or more for younger wines. He is also against removing the deposit because he thinks that this will change the taste, even destroy the structure of the wine. He accepts "that the first glass of wine poured first tastes different from the last".
But also supporters of his method think that the depot should be removed in any case. The effect of the "Audouze method" is that oxygen is very slowly added to the wine (after it may have been deprived of it for decades) and it therefore develops much more harmoniously. The not so rare "decanting shock" can supposedly be avoided by this, which can lead to prominent acidity or hard tannins in older wines. According to Audouze, his many years of positive experience are based on "over a thousand opened bottles of vintages before 1945". These included absolute top rarities dating back to the beginning of the 19th century.
As a résumé, one can only give the advice to try it out for yourself. At best, one enjoys the same wine once decanted and once not decanted - ideally even in parallel - to form one's own opinion. But of course you need two bottles for this, but this creates a "new problem". Wines can develop differently and the same wine can taste differently in two different bottles; this phenomenon is called bottle variance. So again, this is not a clear "scientific proof". A compromise would be to decant half a bottle and leave the other half in the bottle that is to be closed again immediately. But this would not be 100% in the sense of the thing, because even a short contact with oxygen could already cause changes.
The most objective (and also undisputed) reason for decanting is to separate the wine from the depot (polymerised tannins and colourings) deposited at the bottom of the bottle, which is particularly common in red wines, and possibly tartar. Apart from the negative appearance, these would otherwise inevitably get into the glass and possibly negatively influence the taste.
The second and, as described above, not undisputed reason for decanting is to bring the wine into contact with oxygen and to allow its aroma to unfold. The majority of wine lovers consider this method to be very important and useful. This decanting into another vessel for the sole purpose of aeration is also called carafing. According to the advocates, this can change a wine in a decisive positive way. The ceremony requires a lot of sensitivity, patience and time. The bottle is already placed upright two to three days before consumption so that the deposit can collect at the bottom. The bottle can be placed in a decanting basket or Wine Cradle where the bottle is stored with the neck sloping upwards. How long the wine should be decanted before drinking depends on the grape variety and the age of the wine and also on personal experience. Usually it is at least one to three hours.
The cork must be removed carefully without disturbing the deposit. Then you start slowly and calmly on the inner wall of a Carafe to pour in. A decanting funnel can be a good aid to allow the wine to flow directly into the wall. This allows the wine to come into direct contact with oxygen for the first time and begins to develop its aroma. A Decanter enables a smooth and even pouring. The bottle is clamped into the machine with the opening diagonally upwards and the bottle neck is slowly moved downwards by a hand crank. This is useful for certain types of port wine or similar wines, as these develop an extremely fine deposit. When pouring, a light source must be located just behind the bottle shoulder to detect the appearance of the depot, which is presented as a black line. When the first traces become visible, pouring is stopped.
One variant is Double Decanting (double decanting). Here the wine is first decanted into a carafe or an empty bottle. Then the bottle is cleaned to remove any deposit residues and then the wine is filled back into the bottle using a funnel. If the bottle is to be transported, it is closed again. According to the followers of this method, this has several advantages. Due to the double oxygen contact, the wine is "aerated" even better. Bottles pre-decanted in this way can be taken anywhere and are immediately ready for consumption. Furthermore, bottles with the original labels cannot be confused with other wines (bottles), which can only be avoided by marking the carafes with different wines when several carafes with different wines are used.
Unemptyed, undecanted bottles can be stored again without additional effort(wine climate control cabinet or refrigerator). Another advantage could be that bottles with the often elaborately designed labels at the table look more attractive than carafes. Furthermore, everyone can easily read the information on the label. There are also some brand systems or technical devices (so-called mini decanters) that are placed on the bottle. During the pouring process the wine comes into contact with a lot of air or oxygen. These are among others Decantus, Venturi tube and Versovino. There are many other accessories such as a "silver ball" which can be hung in the neck of decanters and allows the wine to flow gently. On this subject, see also aging, bottle aging, drinking maturity, wine enjoyment, wine glasses, wine cellar, wine temperature and wine with food.