Sugar in wine

We’ve already told you in this blog that during fermentation, the sugar in grape must (formed essentially of glucose and fructose) transforms into alcohol through the effect of yeasts. Therefore, the sweeter the must from which wine is made, the greater the degree of alcohol it will have. Simple, right?

But if you are not familiar with this chemical process, you may ask yourself if the wine still contains sugar after fermentation, or if it disappears completely.

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The answer is yes: effectively, the wine retains a certain amount of sugar, in greater or lesser quantity depending on the type of wine. As such, for example, red wines retain very little sugar where as sweet white wines can contain a considerable amount, but why? Pay close attention!

Why wine contains sugar

To understand why wine contains sugar, we must focus our attention on the fermentation process that we mentioned earlier. During this, and when the wine reaches a certain percentage of alcohol, the yeasts die, so they stop converting sugar into alcohol. Therefore, all the sugar that hasn’t been transformed stays in the wine, a part of which is fermentable sugar (glucose and fructose) and the other sugars that the yeast can’t metabolize. The total of this sugar is called residual sugar.

Still wines (non sparkling) can be classified according to the amount of residual sugar they contain:

  • Dry. Containing up to 4 grams of sugar per litre.  
  • Medium dry. Up to 12 grams of sugar per litre.
  • Medium sweet. Up to 45 grams of sugar per litre.
  • Sweet. More than 45 grams of sugar per litre. Some wines contain as much as 200g per litre!

In the case of sparkling wines, the classification is as follows, and depends on the amount of sugar that the liqueur d’expédition that is added contains:

  • Brut nature. Contains less than 3 grams per litre.
  • Extra brut. Up to 6 grams per litre.
  • Brut. Up to 15 grams per litre.
  • Extra dry. From 12 to 20 grams per litre.
  • Dry. From 17 to 35 grams per litre.
  • Medium dry. From 33 to 50 grams per litre.
  • Sweet. More than 50 grams per litre.

This is the reason why red wine (which usually contains no more than 2 grams per litre of sugar) is the most suitable for people who want to limit their sugar consumption, although, as we have already explained, it is never 100% free of it. As I’m sure you’ll also realise, the amount of sugar (and also the level of alcohol) are related to the number of calories that wine contains.

How much sugar does a particular wine contain?

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It is difficult to know how much sugar a specific wine contains, as there is no legal requirement to mark it explicitly on the label and very few do so. Although sparkling wines must specify, at least, what style it is according to the groups set out in the aforementioned classification.

Can you add sugar to wine?

Effectively, some winemakers add sugar to the must prior to or during fermentation to compensate for the lack of sugar or to produce a sweeter tasting end wine.

This technique is known as chaptalization (it was developed by a French chemist named Jean-Antoine Chaptal in the 18th Century) and it is somewhat infamous as, as I’m sure you will have guessed, what it seeks to do is to cover up the fact that the raw material, that is to say, the grapes, were not very ripe.

In Spain, with some exceptions (in the case of occasional unfavourable weather conditions, when a special permit is required), chaptalization is forbidden.

In other areas, where the climatic conditions mean that the grapes don’t reach the optimum level of ripeness, this technique is accepted and more widely used (for example, in Germany and France the technique is permitted) but, as we have already mentioned, it is a very controversial subject that generates quite a lot of debate in the wine world.

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