A Dark Growth Starting in My Ferment

This is my first ferment - a cabbage kraut, it is formulated according to the recipe in the book Farmhouse Culture Guide to Fermenting. I used all the sanitary precautions suggested. The photo below shows a dark growth developing after only four days of fermentation, unfortunately at approximately 72°F which is the lowest I can provide in my home outside the refrigerator. Can anyone diagnose what is happening and let me know if I should be concerned or continue with the ferment?

Thanks for knowledgeable comments,

Peter

I'm not sure about the dark spot. In my (limited) fermenting experience molds are often pinkish. My guess would be it's a bruised leaf expressing itself more clearly now, but it could be otherwise.

I'm a little worried about that air pocket in the jar on the right. Are your leaves fully submerged in your brine? Anything that's getting air to it is much more likely to mold. If it's just a bubble you might need to let the air come to the top.

Looks like maybe black mold.  Probably should discard the affected leaves and make sure rest are submerged.

Hello Peter. I agree with L & MK: submerge, pluck the problem out of the jar. One more thing: lactic acid bacteria thrive in the dark: UV light (sunlight) is a natural anti-bacterial agent. Traditional clay fermentation vessels are dark and, when nestled into the earth or placed on the floor (heat rises, cold sinks) keep contents colder than the ambient air. Your beautiful glass jars could be put in a clay pot for darkness and put on the floor, or put into a water resistant container which you dig into the cool earth. The LAB will be happier in the cool darkness. Good luck and enjoy the experiments!

P.S. To submerge your ferments, put a small glass or ceramic plate on top of the cabbage. Put a clean stone or other weight on top of the plate. Or put a flat clean stone directly on top of the veg.

As others have mentioned, all of the plant material needs to be submerged. This used to be done with a plate with a weight on it if you're doing open fermentation in a barrel or bucket. I do the jar with airlock now, like you're doing and there are glass weights you can use that are helpful but don't always do the trick.

The jar on the left with the black growth has a lot of cabbage that is not submerged. All of the discolored kraut needs to be removed and the rest of it checked for taste/odor.  Sometimes the cabbage is drier than usual so you don't get enough juice to keep everything submerged so when that happens I add brine (50g salt/liter) to top off the jar. We drink a shot of fermentation juice in the morning so extra juice doesn't go to waste.

Good luck with your fermentation endeavors. I've ruined plenty of jars of veggies when I first started learning, especially since I like to experiment. When you get it right though, it's wonderful.