How long will an opened jar of fresh sauerkraut last? I bought a jar that was in the deli section at the grocery store to make Reuben sandwiches and now have 3/4 of the jar left.
I'm not sure if there is any real agreement about this, but I think unless your sauerkraut has ingredients other than cabbage, salt/vinegar and water, it should last indefinitely. Sauerkraut is fermented cabbage, and the organisms that cause the fermentation also keep it from spoiling. (In fact, sauerkraut is a suggested food, along with yogurt and acidophilus, for keeping your digestive tract healthy.)
I buy fresh sauerkraut at one of the greenmarkets here in Brooklyn (Dr. Pickle), and I asked them about storage, They said that fresh sauerkraut should keep indefinitely in the fridge. I've used sauerkraut that I've had for weeks (maybe 6, maybe 8 weeks, even longer) with no problem.
Suggestion for you: cook a couple of hot dogs in one pot (you can simmer them in water to cover), and for accompaniment take some of that sauerkraut and add a little water and a tablespoon or so (doesn't have to be exact) of plain vinegar and bring it to a simmer. Slather some of your favorite mustard on the hot dogs and eat them along with the sauerkraut. It's comfort food (at least for me), and you'll be doing your digestive tract a solid favor.
If you're not comfortable with the kraut, you can always toss it and buy some more, but you really don't need to.
Good luck in any event...