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What is Residual Sugar in Wine?

Good news for all those closet sweet tooths out there, it’s OK to like sweet wine! Residual sugar is back on trend and making a resurgence in popularity. In fact some of the most highly regarded wines in the world have some sugar in them – think German Rieslings and French Sauternes. This article explains what residual sugar is and the types of wine it features in.

What is residual sugar?

The sugar in grapes ferments into alcohol (see our article How do winemakers know what the alcohol content will be in wine? for more details), but when the ferment stops (for reasons explained below) before all the sugar is fermented it leaves some residual sugar (hence the name).

This can happen for a number of reasons, including:

  • The winemaker will stop the ferment as they desire some residual sugar
  • There is so much sugar that the yeast can’t ferment it all

More details below.

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We were lucky enough to do a vertical tasting of these beauties from Marcel Deiss, Alsace

Off dry/semi sweet/medium dry wines

These are wines that have just a bit of sweetness, but are by no means dessert wines. Winemakers stop the ferment while there is just a hint (or a bit more than a hint) of sweetness.

A great example of this is German Riesling. Generally speaking, German Rieslings have at least some residual sugar, whereas most Australian Rieslings are bone dry with no RS. The sugar in these wines is balanced by acidity so in many cases it is not apparent. It is not always easy to know how sweet a german riesling will be, however if you see the word trocken on its own this indicates a dry style.

These varieties are often made in a sweet style:

  • Riesling (particularly from Germany and New Zealand)
  • Alsace blends
  • Gewürztraminer
  • Loire Valley whites (labelled sec or moelleux)
  • Moscato
  • Brachetto

Chateau d’Yquem is the world’s most famous (and expensive) Sauternes

Unfortified Dessert wine

Unfortified dessert wines can be produced in a number of ways, but always have too much sugar for the yeast to ferment. Techniques include:

  • Late harvest: grapes that stay on the vine for longer become more like a raisin with more concentrated sugars.
  • Noble rot/Botrytis: is a type of mould that rots the grapes, it looks and sounds pretty gross but produces a wine that has honey notes.
  • Ice wine: in colder wine regions in extra cold years the vineyards freeze (famous examples are from Germany, Switzerland and Canada). This happens because the water in the grapes freeze but the sugar does not, meaning much more concentration when pressing.
  • Air-drying: some climates allow for grapes to dry and raisin after they are picked. This evaporates some water, concdentrating the sugars and solids.

Famous example of above include:

  • French Sauternes
  • Hungarian Tokaji (Tokay)
  • German sweet Rieslings (trockenbeerenauslese)
  • Vin Santo and Recioto from Italy and Vinsanto from Greece

There you have it, a guide to residual sugar in wine.


You might also enjoy:

What is the difference between red and white wine?
What’s in my wine? (what are the additives in wine?)

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