It is frustrating when waiters ask me if I want a dry wine and when I say "yes", they continue by saying this wine is drier than that one, when I know that both wines have been fermented to a bone dry condition. I think waiters should learn other ways to describe wines and not misuse the word "dry".
All Jarvis wines are "Bone Dry." The term "dry" , in reference to fermentation, technically means that there is less than 1% residual sugar in the wine. Most people generically use the term to describe a wine in which there is no perceptible sweetness. However, a wine can be fermented "dry" and still taste slightly sweet due to other factors I will mention later.
During the fermentation process the yeast that consumes the sugar in the grape juice producing alcohol and CO2. The yeast will continue this process until all of the grape sugar has been used up at which point, having no food source, the yeast cells die and become the lees. Wine is fermented to dryness because, among other things, leaving sugar in it would make it microbially unstable. Residual sugar n a wine which contains less than 16% alcohol creates a substrate for possible yeast growth, making the wine potentially unstable or liable to re-ferment in the bottle.
Most enologists consider primary fermentation as complete when residual sugars are in the range of 0.1-0.2%. Usuing the reducing sugar measurement, wines below 0.2% are generally considered stable in the regard to the possibility of re-fermentation in the bottle. At this point most of the residual sugars present are pentoses (monosaccharides) which are unfermentable by saccharomyces yeast. However, it is possible for microbial activity to occur even when sugars are at less than "dry" levels. Brettanomyces, a spoilage yeast, can utilize residual sugars well below the 0.2% level.
The standard range of residual sugar for table wine (wine you drink with dinner) is 0-3%. The following is a typical scale used to classify the sugar level in wine.
Residual Sugar Technical Classification
<0.5% bone dry
1-2% semi-dry (medium dry)
2-3% semi-sweet (medium sweet)
It is a misconception that dry wines cannot taste sweet. The sweetness of a wine on the palate is greatly influenced by the level of glycerol, alcohol, acidity, and tannins in the wine. Even the serving temperature of a wine can affect how sweet it tastes.
So, a "bone dry wine" with a residual sugar level of less than 0.2% but one that is relatively high in alcohol and glycerol can actually taste somewhat sweet.
Sweet dessert wine can range from 1.2% to 20% residual sugar. In wines such as Sauternes where the grapes are picked at very high brix, fermentation stops at about 15% alcohol as the alcohol begins to act as a preservative drawing all of the water our of the yeast cells. In the case of Port wines, alcohol is added to the wine to stop the yeast fermentation.
The post fermentation integration of grape sugar is not uncommon. Grape sugar masks the effect of acidity and tannin in a wine. Sometimes, grape sugar is added back after fermentation to disguise (hide) defects in lesser quality wines. That's why "jug" wines are usually fairly sweet - to hide flaws caused by using inferior (less expensive) grapes.