Q: I would like to sweeten some red wine that has gone through MLF. I know that I need to prevent renewed fermentation. Will sulfite prevent renewed fermentation? If so, what concentration of free sulfur do I need?
— Greg Farke • Armour, South Dakota

A: It seems that you and Craig are going through many of the same issues (see this question and answer). Like I mentioned to Craig, it’s really impossible to add enough sulfur dioxide to retard a yeast fermentation because, contrary to popular belief, yeast just aren’t that sensitive to SO₂. Unlike bacteria, yeast can still have a wide range of activity at high levels (even above 50 ppm FSO₂) in juices and wines. Depending on your sensitivity, you may start to smell the FSO₂ at levels of 30 ppm and above. Don’t forget that even a small amount of carbon dioxide, like that produced by a partially-viable yeast cell, will amount to a “flaw” or defect in your still red wine.

I am a proponent of sterile filtration if you can rent one from a winemaking supply store or share the cost of one with some winemaking buddies. If you want to get beyond making wines that are “primary fermentation dry” it might be a piece of equipment you should budget for. Barring that, I really think adding sorbate might be your only option. Yes, there is a chance of developing a geranium off-odor, but some people don’t think that’s the end of the world. If your alcohol is 12%, you will add 100 mg/L potassium sorbate. If it’s 14% you can get away with 50 mg/L. If you aren’t into dosing with sorbate, you may have to decide if you’d prefer a sparkling red sweet wine.