Sugar In Wine

sugar wine

There is one simple equation in life that every wine lover must know: without sugar there is no alcohol. As previously mentioned in several posts, it takes sugar to make the alcohol that so many of us love and quite possibly live for. And thankfully wine grapes have plenty of it. The sugar in wine is converted to alcohol during the fermentation stage of winemaking. During the growing season the hanging grapes develop moderate sugar levels as a result of translocation. This is the transfer of sugars from one location (the leaves) to another (the grapes). Some grapes will have more sugars than others, depending on hang time, but the sugars are produced during photosynthesis in all cases. This is really interesting I know, but bear with me, it doesn’t get any more exciting. Really.

So once the grapes have ripened on the vine, the sugar levels make up to 25% of the grapes composition. The rest is water and pip, skin, seeds…. And only a few of the sugars in the grape are fermentable; these are glucose and fructose, preservative favorites. The non-fermentable sugars are not very popular, mainly because, well, they can’t make alcohol. They are aribinose, rhamnose and xylose. It’s because of these last three sugars that you can never have a completely dry wine.

However, sometimes there isn’t enough fermentable sugar in the grape must and the wine doesn’t get as dry as the wine maker intended. When this happens, he can add sugar to the must in the process of chaptalization to achieve a greater dryness. This allows more sugar to ferment and raises the alcohol content to the desired level the wine maker set out to achieve. Chaptalization is done typically for a harvest that doesn’t reach full maturity (measured in Brix) on the vine.

Residual sugars are beneficial to wines and can be pivotal to producing a fine wine. When it comes to something like a German Riesling, which has high acidity, residual sugar can provide a nice balance. The elevated sugar content in wine can hide flaws, like bitterness. And with low end wines that are somewhat flat (also called dumb) and lackluster, adding residual sugar in wine can add flavor.

When the level of wine sugar content has to be raised there are two ways this can be achieved. One is to simply stop the fermentation process. This might sound complicated, but all the wine maker has to do is chill the wine and filter the remaining yeast out of the must or, another way is the must can be fortified with brandy spirits. An alternative to this, because of the low sugar content in alcohol, is to let the wine ferment to dryness and introduce unfermented juice to the must. For the true wine geeks out there, this process is called sussreserve; it’s a German term.

Sometimes, though, a wine just will not ferment to the desired level. Certain things like pesticides or crappy yeast, rot or too hot of fermentation temperatures can prevent sugars from fermenting to their maximum potential, this is especially crucial when trying to ferment the sugar in red wine. When this happens it is called stuck fermentation.

Looking back to the fructose and glucose that make up the fermentable sugars in wine, it might be interesting to know that though both sugars have the same concentration levels, they are not both equal in sweetness. Fructose has twice the amount of sweetness as glucose. What’s strange is that during fermentation, glucose is the first to be converted, so you’re left with more fructose by the end of it.

Depending on how the wine was finished, you could have two different tasting wines. Taking the same juice, in the process of arrested fermentation where you do not process out all of the sugar, wine comes out tasting sweeter; whereas a wine of the same juice that has had residual sugar added back in will seem less sweet. Why is this? Because, the fructose is the last of the wine sugar to be processed and since fructose is sweeter than glucose, the resulting wine will taste sweeter if the fermentation was arrested.

So, from this you can see the tremendous role of sugar in wine and how without it, there wouldn’t be a wine press blogger.

Sugar Content in Alcohol Sugar
Red wine, 100 ml 0.62
White wine, 100 ml 0.22
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