Carbonic acid | All about champagne

In colloquial language, carbon dioxide (CO2) in the Sparkling wine commonly referred to as carbonic acid (H2CO3), although only a relatively small proportion of the carbon dioxide (CO2 ) physically dissolved in the wine actually 'marries' with the water or causes actual carbonic acid (H2CO3).

As the name suggests, carbon dioxide has a slightly acidic effect. This in turn influences the perceived sweetness of a sparkling wine (the officially permitted limits for residual sugar levels can therefore be higher for sparkling wines due to the relatively high carbon dioxide content).

Carbon dioxide also emphasises some of the flavour components of a wine, such as acids and tannins. For this reason, many connoisseurs avoid drinking certain mineral waters before or during a tasting, as they are often not neutral in flavour (minerals) and contain more or less carbon dioxide. The carbon dioxide therefore influences the flavour perception of the tasted wine. The wine could, for example, appear more bitter or more acidic than it actually is in terms of acidity. As a result, mineral waters with minimal (or no) carbon dioxide and low mineral content (less than 500 milligrams of minerals per litre) are often preferred. Many wine lovers also simply stick to tasteless tap water before/during a tasting. The decisive effect of CO2 and carbon dioxide on flavour is illustrated by tasting sparkling wines (or even a 'cola') after opening a few days later without carbon dioxide. The carbon dioxide quickly dissipates. As soon as the sparkling wine is stale (worn out, dead, passé, 'flat'...), it appears (sometimes considerably) sweeter.

According to a study by the University of Surrey in Guildford, UK, carbon dioxide/CO2 is said to contribute to the alcohol concentration in the blood (see links below). One test group was given stale Champagne served. After five minutes, the group with the proper champagne had a blood alcohol level of 0.54, while the test group with the discarded champagne only had 0.39.

CO2 content in sparkling wines is primarily produced by three processes:
1. by impregnation or the addition of (foreign) CO2 gas.
2. by first fermentation, whereby CO2 produced during the fermentation of must is only partially or completely kept in stainless steel tanks.
3. through a second fermentation, whereby an already fermented still wine is turned into sparkling wine by means of a second fermentation in the bottle (bottle fermentation) or in a stainless steel tank (large-capacity fermentation).

For champagne (only pure bottle fermentation is permitted), the process is as follows:

After blending, a mixture of wine, sugar and yeast is added to the wine before it is bottled for the second fermentation. This filling dosage ("liqueur de tirage", not to be confused with the dosage made before the final corking, the "liqueur d'expedition") is crucial for achieving the correct carbon dioxide content in the end product. The development of carbon dioxide/CO2 is completed within around seven weeks. A typical champagne (or sparkling wine) therefore has an overpressure of approx. 5-6 bar, which allows a lot of CO2 (approx. 9 grams per litre) to be retained in its water-soluble form. The CO2 also dissolves more favourably in the chilled wine and can be kept longer in the H2CO3 form (one reason why champagne should be served chilled). It should also be noted at this point that the custom of placing a silver spoon in the neck of an opened bottle in the fridge offers little to no advantage in terms of preserving the precious bubbles. The advantages of the silver spoon as a heat conductor are irrelevant. A study by the magazine 'New Scientist' tested this with two opened champagnes (one with, one without a spoon). The perceived carbon dioxide/CO2 was exactly the same for both bottles on the following days. Only after more than four days were both champagnes completely stale or 'flat'.

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