OK, we grew up in NYC, and as we grew up we found kosher delis. Did not know each other then. But a very common experience here.
In the delis found the most wonderful hot dogs. But the one thing definitely remember was the kraut. Growing up had always had the very tart stuff, from a can or bag.
But the kosher delis had something that was less sour, somewhat more firm, and great.
Then we were able to get it in jars in the supermarkets, but always cold.
And have a few times, as we have moved about a bit, found the stuff there and there.
Unfortunatley cannot find it here.
Once, several years ago, took a tried-and-true recipe from a respected book and tried to make the stuff.
When we looked at it after the suggested fermenting time, it was only a couple of days, really, well, I don't know what they call black fungus but it was not not anything you would want in your house. We put it in the backyard, hoping the moles would eat it.
Great mole food, I can only guess. They grew like crazy after that.
Assume, like many other folks here, it is fresh, new kraut. Sorta like the European version of kimchee.
But don't remember the carbon dioxide bubbles that I find in Kimchee.
Love the stuff.
Don't know why we only found the new kraut in areas that had many kosher food stores.
To the best of my limited knowledge on kosher requirements, kraut is just hunky dory, I would guess except during Passover (the yeast).
Anyway, that is all we can add.
Know it is not much, just wish we understood more.