I just joined a long time wine making group and we have a question about when to add sulfur/sulfites for our red blend. We started the malolactic fermentation about 3 months ago and it has been going slowly. We did paper chromatography testing about a month or so ago and it was showing malic acid levels below 0.3 which is the lowest level of sensitivity for this test. However, we can still hear the crackling in the casks, so were concerned that the malolactic fermentation has not completed, and we understand this is a real no no. Others in the group are a bit less concerned and want to add now. A winemaker friend has suggested that we get it down below 0.05.
Sometimes my MLFs finish in late February here in California. If you want a stable wine that won’t referment in the bottle it’s always a good idea to be sure that malo is complete. I would just keep it topped up every week to prevent VA. If you can stir the cask and get it a bit warm it may speed up the process.
Thanks so much for the advice - we were racking the wine among barrels and a couple of them tasted a bit fizzy and we could hear crackling, so we ran the malic acid numbers and it showed that a couple of barrels were at .12. We added sulfite to all but 1 of the barrels, but are going to wait for the last one, and then try to start ML fermentation for the sulfited barrels after they settle down.