Questions regarding "but added 2 c. sugar/1 c. water syrup to bring the SG up to 1.090." I have done three dessert wine kits, which required chaptalization (dissolved the contents of the chaptolization pack (400 g Dextrose TPH) in 350 ml (1.5 Cup of hot water) and added to primary fermentation bucket. But, this was after the first 5-7 days of primary. And, one of the kits came with two packets of yeast. So, (1) what is your thinking about the timing of chaptalization, and (2) how do you know if you have enough yeast to process the extra sugar?
- Mark, a relative newbie just starting 9th batch ... a So African Sauv Blanc
I'll explain in a moment why your kit instructions had you add your sugar later, but first let me point out that Donatelo is only trying to bring his ABV up to ~13% or so. Normal wine yeast can handle that pretty easily, so the timing does not matter too much.
For your case, there are two reasons that the chaptalization is delayed. For a dessert wine, you want the ABV to be very high. That means a lot of sugar. If you add it all in at the beginning, the environment will be hostile to yeast -- too much of a good thing. The high sugar levels negatively affect the yeast.
The second factor is that they are having you add, not sucrose, but rather dextrose. Why dextrose? It would be cheaper to add table sugar (sucrose). Well, sucrose is a disaccharide, which means that it is essentially two sugars bound together. When it splits, it splits into glucose (aka dextrose in this case) and fructose. Our pet yeasts can metabolize either of these monosaccharides, but they have a much easier time with dextrose. The idea is that during your initial fermentation (for the first 5-7 days), the yeast eat nearly all the fructose and/or dextrose present; in the process, they produce alcohol. They produce so much alcohol that the must is now starting to become a hostile environment; however, you still want to give them
more sugar so that they can produce yet more alcohol. So you decide to make it as easy on them as possible, since they are under stress, so you feed them dextrose.
If you instead added the chaptalization pack in the beginning, the yeast would likely have eaten all the dextrose before getting through all the fructose. Then they would be struggling to metabolize the fructose when they were in a very hostile environment, making a stuck fermentation more likely.
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