Two kilos of cabbage at 2 percent salt, glass weight, jar with a loose lid, sitting at about 21C. Day five there is a thin white film across the whole surface of the brine, flat and slightly wrinkled, no fuzz that I can see and no colour to it. It smells sour and cabbagey, not musty. Everything under the brine looks normal. Do I skim it, stir it in, or bin the whole jar?
One safety line I hold to regardless of what a photo looks like: if there is fuzz, if there is colour, or if it smells of wet basement rather than sour, the whole jar goes out. Kraut is cheap and I am not clever enough to identify mould species at a kitchen counter.
For anyone finding this later: two weeks on, the kraut is sour and crunchy and there was no further drama after skimming.
The two things that reliably give me kahm are too warm and too much air above the brine. 21C is on the high side for kraut, I get much cleaner ferments around 18C, and it also stops the cabbage going soft. Not urgent, just the reason it keeps appearing.
Salt matters too. 2 percent is the low end for kraut at room temperature, and 2.25 to 2.5 made mine noticeably less prone to film.
Fitting a smaller jar of water on top as a follower keeps everything submerged better than the glass discs, which tend to let a leaf float up round the edge. That floating leaf is usually where the film starts.
@iris_tanaka · 5mo ago · 3 replies
Flat, wrinkled, white, no fuzz, smells sour rather than musty is kahm yeast, and it is harmless. Skim off what you can with a clean spoon, do not stir it in because it tastes faintly of nail varnish and will carry through, and make sure everything stays under the brine. Mould looks different in a way you will recognise instantly once you have seen both: it is fuzzy and three dimensional, it grows in distinct round colonies rather than an even sheet, and it comes in colours, blue-green, black, pink or grey-white with visible texture. If any of that appears, the batch goes.
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@waterbath_wes · 5mo ago
Definitely a flat sheet, no colonies. Skimmed it and it was back thinner by the next day.
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@iris_tanaka · 5mo ago
Normal. Skim every day or two, or just leave it and skim once at the end. It slows down when the pH drops further. Colder ferment and a fuller jar with less headspace both discourage it next time.
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