I've been fermenting a batch of sauerkraut and it's been going for about a month. It's tasted great and has just recently started to develop some winey flavors.
Today I checked the crock and there is a strong sweet smell that reminds me most of those cinnamon-sugar pretzel places that they put in malls and airports. The kraut is still fine and doesn't taste sweet except for the smell.
The only thing in the kraut was cabbage and salt.
Best Answer
In my experience a month is a bit long (although of course this depends on the size of the batch, etc) for active fermentation - however I don't think that's the problem. In fact, I don't think there is a problem. Since Sauerkraut is a 'wild' food, there are some variables that you can't (and shouldn't) control.
The most likely (85% sure without knowing other factors) situation is that your kraut has picked up an uncommon variety of wild yeast and that yeast is doing its thing and putting-off this sugary/sweet smell as a byproduct of its processes.
Are you doing anything different with this batch that you've not done in the past? Fermenting it in a different part of your house, maybe? Is the temperature unseasonably warm/cold? Regardless I think you'll be safe and come out with good kraut (which doesn't seem to be your concern) - but if you come out with REALLY good kraut, maybe you'll want to try to duplicate your experience :)