What is Residual Sugar in Wine?

One of the terms that gets thrown around in the wine world is 'Residual Sugar.' But it's not something you are going to read about on a wine's label. So, what is it and why should you care?

Let's take a quick step back and review the basics of the wine making process. Simply put, grapes are grown, picked, crushed and fermented into wine then aged and bottled. It's the fermentation process where sugar comes in. 

Grapes naturally contain various types of sugar. Glucose and Fructose are the two most common sugars, but there are others. Grapes also contain varying levels of sugar. Grapes that are allowed to fully ripen, in warm climates, will contain more sugar than grapes that struggle to ripen in cooler climates. And, wine makers will closely monitor the sugar levels (Brix) in grapes while still on the vine, and choose to pick their grapes when the sugar levels are 'just right' for the grape-type they are growing and their style of wine making.

During the fermentation process, yeast is added to the sugary grape juice. The yeast feeds on the sugar and produces alcohol. If there is any sugar remaining after fermentation, it is referred to as 'residual sugar' (usually noted as RS) and is typically recorded in grams per liter (g/L). This is somewhat of a technical term for a wines' resulting sweetness.

Residual sugar is one component that can contribute to a wine tasting sweet. Next time we'll further explore sweetness in wines.  Until then, Cheers!