Sugar content in wines – how does it work?

Grape harvesting has just finished. Maybe you could see on Facebook of some wineries “strange thermometer” showing the value around 20°. And the more experienced wine lovers suspect that it is a standardized mustmeter, which is used for determination of the amount of natural sugar in grapes. The amount of natural sugar is an indicator of the grapes ripeness.

This value is very important for winemakers, who decide to make high quality wines with special atributes. It indeeds determines, how the wine will be classify. We are still talking about natural sugar, because chaptalization is not allowed for high quality wines. Here in the Czech Republic, the whole process of producing high quality wine is also controled by inspector from SZPI (goverment organization).


The degress of classification

Kabinet – 19°

Pozdní sběr (Late harvest) – 21°

Výběr z hroznů (Selected harvest) – 24°

Výběr z bobulí (Berry selection) – 27°

Výběr z cibéb (Dry berry selection) – 32°

Ledové víno (Ice wine) – 27°

Slámové víno (Straw wine) – 27°

The final sugar-content in grapes is influenced by the weather in the time of grape ripenning. Warm and sunny days with enough moisture are optimal, so the amount of sugar can increase very quickly. The grapes seem to be ripen from the sugar point of view, but there are often missing aromatic substances, which are generated later  – at the turn of September October thank to cold nights. So the main goal of winemaker is to slow down the rise of sugar.

Sugars are generated in leaves during the process of photosynthesis and are transported from leaves into grapes. The increase of sugars can be therefore influence by de-leafing. De-leafing leads to reduction of asimilation surface and accordingly also increase of the photosynthetic activity. So the grape ripening will be put over into later period, which is more favorable for creation of aromatic substances.

Winemakers had to solve this problem for example in the year 2011. The grapes of naturally aromatic varieties such as Sauvignon, Pálava and Gewürtztraminer had high sugar-content at the beginning of September. But wine maked from thus early harvested grapes had not typical varietal atributes, it showed more herbacious an green aromas and was not harmonic.

As you can see, it is a pretty hard work to make high quality wines and it also needs high experienced winemaker. And it seems, that Moravian winemakers belong to this group, because their wines are more and more awarded in many international competitions.

So follow me and you can enjoy these nice Moravian wines during some future event.