Technical problems with fermentation

I have pretty good success making saurkraut with cabbage. But I really wanted to make the fermented dark greens - gundru. It totally failed - rotted. Have you any advice? (It was 2 years ago, I don't remember details of what mistakes I might have made, and you can just tell me to follow the directions.)

Also I wonder about the longevity of my sauerkraut. I have some from last fall in my refrigerator that seems still okay, while some rotted (changed color and smelled different). At what point should I throw them all away?

I also wander what is the difference, and what MAKES the difference, between fermented and rotted...

It's hard to diagnose the problem without a clear description, but try to review the process and try again. The biggest factor during fermentation as well as storage is that the veggies be submerged. When they start to discolor in the fridge, that suggests a mostly empty jar with lots of air space. A strategy for lengthening the life of your kraut would be to consolidate into a smaller jar and press down to submerge. Discoloration and funky growth comes from oxygen. Protected from oxygen, in a cool spot, mature kraut can last for years.

As for the difference between fermented and rotted, generally the biggest difference is intention. It's a ferment when the changes are desired and intended, rotten when not. There are man fermented foods eaten around the world that people who have never encountered them would generally reject as rotten, such as buried fish in the Arctic, surstromming in Sweden, stinky tofu, natto, strong ripe cheeses.... There is a large component of cultural relativism in our distinctions between fermented and rotten, and no sharp scientific line.

Sandor Katz wrote:There are man fermented foods eaten around the world that people who have never encountered them would generally reject as rotten, such as buried fish in the Arctic, surstromming in Sweden, stinky tofu, natto, strong ripe cheeses.... There is a large component of cultural relativism in our distinctions between fermented and rotten, and no sharp scientific line.

One of the worse seems to be the Tahitian fafaru...

http://www.gonomad.com/features/0101/brash_fafaru.html

The fish is fermented in shrimp fermented sea water...
It is supposed to smell like the most rotten carcass and thankfully have a different taste!

Sandor Katz wrote:There are ... fermented foods eaten around the world that people who have never encountered them would generally reject as rotten, such as ... strong ripe cheeses

A French lady who supports schools here in Ladakh got a good donation from a major cheese company. Aside from the money, as a friendly gesture they sent many packets of their famous blue cheese, I think it was Gorgonzola, to Ladakhi families — who opened the packages with horror and quickly disposed of the smelly moldy contents before it could infect their dairy products.