by Howie Hart » Thu Sep 20, 2018 6:40 pm
I've been thinking about an aspect of the subject for the past few days that is not mentioned: the sugars in wine. Common table sugar is sucrose, a di-saccharide consisting of glucose molecule (6 carbon sugar) bonded to a fructose molecule (5 carbon sugar). Grape sugar consists of the same two molecules, in the same proportion, not bonded together. In the presence of yeast and the acid in the wine, sucrose will break down into the two components. The sugar content of the juice and the resulting increase of alcohol in the wine, can easily be increased by the addition of sucrose, with little effect on the other flavors. It's the same with sussreserve, when juice at pressing is reserved and added back to the wine prior to bottling for sweetening: glucose + fructose. When a wine has "residual" sugar, this implies that the fermentation was stopped prior to going completely dry, but often, sucrose is added to the wine prior to bottling. There is a subtle difference in the mouthfeel of wines made these two ways. This is because during fermentation, yeast has a preference for the glucose and consumes it first, leaving fructose for the latter part of fermentation. The glucose and fructose act differently in the mouth. The glucose can be cloying or syruppy, while the fructose gives a sweeter impression and a cleaner mouthfeel. In 2013 I did an experiment with Riesling. I fermented normally until just over half the sugar had been consumed. I removed about 15% of the batch and froze it. The rest of the batch continued fermenting to completely dry. Then, several months later, just prior to bottling, I added the partially fermented wine back into the batch, filtered and bottled it. The resulting wine had a much higher concentration of fructose than glucose, so it tasted a bit sweeter and had a clean finish. Tomorrow I will be getting my 2018 Riesling grapes from a local grower and plan on repeating this partial sussreserve.
While this example is a bit narrow, the other things mentioned (acidity, tannins, etc.) may all have subtle tweaks to the process that change the "texture".
Chico - Hey! This Bottle is empty!
Groucho - That's because it's dry Champagne.