Originally Posted by sashurlow
First off, I'm using a keg, so carbonation is taken care of. I have alreay backsweatened my graf with non-sulfited AJ concentrate and the sweetness slowly fermented away. If I use sulfited AJ will it stay longer or always?
No. Sulfites don't affect yeast.
In order to sweeten, and not have fermentation recur, sorbate is used when the cider is clear and before sweetened. Sorbate keeps yeast from reproducing, so fermentation can't restart.
Normally, a clear cider is racked onto sulfites (campden) and sorbate and then allowed to sit for a few days. Then it is sweetened to taste. Most of the time, fermentation doesn't restart after stabilizing.
Keeping it cold, as in a kegerator, also can slow down the refermentation if it does start up again.