residual sugar, occasionally RS, the total quantity of sugars remaining unfermented in the finished wine. This may include both fermentable sugars, mainly glucose and fructose, which have for some reason remained unconverted to alcohol during fermentation, and small amounts of those few sugars which are not readily fermented by typical wine yeast. Some, but by no means all, residual sugar is tasted as sweetness. reducing sugars, a term used by both the eu and the oiv, refers to all the sugars measured in a finished wine, including residual sugar and any sugars added post fermentation, for example, in the form of süssreserve.
