My cherry berry wine has been in the primary fermenter for 11 days. It’s been 4 days since any significant activity was seen in the airlock and I think it’s time to rack it to secondary. Most country wines don’t benefit from spending much time on the lees — the winemaking term for the yeast sediment at the bottom of the fermenter. In beer, we’d call it trub.
The day I made the wine, I added 1 Campden tablet per gallon (3.8 L) to the must (the unfermented wine). This should have added 66 ppm sulfur dioxide (SO2) to the must, initially. When you add potassium metabisulfite (the active ingredient in Campden tablets), it releases some sulfur dioxide SO2 gas, the so-called free SO2. The rest of it remains dissolved, in one form or another, in the must. The percentage of the metabisulfite you add that ends up being released as free SO2 depends on the pH of the wine. The lower the pH, the less metabisulfite is needed to protect the wine. I didn’t take my initial must pH, so I don’t know what percentage of the 66 ppm SO2 existed as free SO2.
Sulfur dioxide at around my initial concentration serves two purposes — it kills microorganisms in the must (because wine musts are not boiled as beer worts are) and it protects the wine from oxidation. The next day, the level of SO2 is supposed to drop low enough that you can safely pitch your wine yeast. This must have happened because I added the yeast that next day and fermentation was in full swing within 24 hours. (I wasn’t watching it like a hawk, so I don’t know exactly when the airlock started gurgling.)