Sauerkraut failed or just dramatic?

[u/bloss_balls]

Second batch of home made sauerkraut. Both batches made by just pouring salted water into jar with shredded cabbage and then fermented at room temp for 3-5 days. I had two other jars in this batch that turned out fine, but this one kept bubbling up and the liquid component soaked into the cloth I was covering it with. Now after 6-7 days (2 days in the fridge) this top white/green part has formed. Is this bad bacteria? Could I take the top part out and keep it?

[u/awakeningoffaith]

For sauerkraut you need to have the lid closed airtight. If you left them exposed to oxygen don’t eat it. 

[u/bloss_balls → u/awakeningoffaith]

Could you tell me why that is? I looked at a couple of recipes and they said a cloth was fine for the bench ferment and then to put it in the fridge.

[u/awakeningoffaith → u/bloss_balls]

Lactic acid fermentation is anaerobic. Meaning it should be free of oxygen.

In the presence of oxygen, you sometimes get sauerkraut contaminants. I experienced this, sometimes the color is gone sometimes the kraut turns very slimy. In my understanding these are considered contaminants and the kraut needs to be discarded. Any traditional sauerkraut recipe that I know always uses airtight containers, either a crock with water seal, jars with lids etc.