FAQ
What can I do about grapes with high sugars?
George Gibson replies on October 7, 2003.
Keep in mind that the high sugars we are experiencing from Black Sage are not an indication that the grapes 'got away' from the grower. They are being allowed to hang to develop flavour complexity and ripe tannins. In a cooler fall the numbers would be in better balance but this fall's unusually hot weather has resulted in a numerical imbalance when they're judged ready to harvest.
Here's how I approach the high sugar situation. First, water your must to bring it down to about 24 Brix. Either use a rough calculation based on percentage or take a measured sample of juice (e.g., 1 litre) and add measured volumes of water to it until you reach 24 Brix and then multiply by your expected yield for the whole batch. If basing your calculations on percentage and you want to water down 26 Brix to 24 Brix, then 2/24=8% is your rough factor. Eight per cent of 25L (100 lbs blacks) = 2.0L water to add. This will mean a final volume of 27L so if your original acid is 5.0 g/L then your final TA (before MLF) will be about 4.6. So if you want to bring your TA up to a better level (say, 6.5) and bring your pH down, add 1.9 x 27 = 51 g tartaric.
High sugar musts tend to be low in nitrogen, so use about 10% more Go-Ferm and about 10% more yeast. Add DAP at about 0.5 g/L after about 12 hours and again a day or so later. (That should add about 100 mg Free Ammonia Nitrogen.) Add Fermaid K at 0.5 g/L when 1/3 of sugar consumed (around 1.070-1.050). (That should add about 50 mg Nitrogen. Adding a total of 150 mg Free Assimilable Nitrogen should be enough for low nitrogen musts fermented with high nutrient-hungry yeasts. Lower sugar musts and/or low nutrient-neutral yeasts should need 50% of those amounts, at most.) Never add nutrient below 1.050.