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Troubleshooting · Updated on 9 October 2026

Sauerkraut and fermented vegetable problems: mould, film, soft or pink

Mould, white film, soft, slimy, pink or dark sauerkraut and fermented vegetables: what each sign means, how to prevent it and when the batch must go.

The methodRecord the batch

Most problems with fermented vegetables come down to salt, air and temperature: too little or unevenly mixed salt, vegetables floating above the brine, or a room that is too warm. 1 Extension guides do not all agree on mould and pink kraut; where they differ, we follow the stricter advice.

Flat white film on the brine

Likely causes

  • Surface yeast, encouraged by air reaching the brine 2
  • Not enough weight or brine cover 4

What to do

  • A flat white film of yeast is not harmful: remove it 24
  • Make sure the vegetables stay under the brine 4
  • If it is fuzzy, raised or coloured, it is mould: see below

Fuzzy or coloured mould

Discard the batch. Do not try to rescue it.

Likely causes

  • Air reaching the surface, poor covering or a warm room 1

What to do

  • Discard the batch; we follow the guides that treat mould on fermented vegetables as unsafe 2
  • Keep the vegetables 1–2 inches under the brine and use a brine-filled bag as the weight 43

Soft kraut

Likely causes

  • Too little salt, below 1.7% 1
  • Salt not mixed evenly, air pockets or a room above 24 °C 14

What to do

  • If it smells and tastes cleanly sour and is not slimy, it is a quality problem; if in doubt, discard 1
  • Weigh the salt, mix it evenly, pack firmly and ferment cooler next time 54

Slimy kraut or brine

Discard the batch. Do not try to rescue it.

Likely causes

  • A room that is too warm, or too little salt 1

What to do

  • Discard the batch 12
  • Use 2.25–2.5% salt and ferment at 21–24 °C or cooler 54

Pink kraut

Discard the batch. Do not try to rescue it.

Likely causes

  • Yeasts growing on the surface, from too much or unevenly mixed salt (over 2.25%) or poor covering 21

What to do

  • Discard the batch: one extension guide treats pink kraut as unsafe 2
  • Mix the salt evenly and keep the cabbage well covered 1

Dark or brown kraut

Likely causes

  • Cabbage not trimmed and washed, uneven salt or a warm room 1
  • Long, warm or bright storage, or contact with metal 12

What to do

  • Darkening alone is usually a quality problem; if it also smells off or is soft and slimy, discard 13
  • Trim and wash the cabbage, avoid metal containers and store the kraut cold 45

No bubbling or no souring

Likely causes

  • A room below 16 °C (60 °F), where kraut may not ferment 4

What to do

  • Move it to 16–24 °C 4
  • If it smells off, discard rather than wait

Change one thing at a time

When a batch disappoints, compare it with the method, change one variable, and note the result in a Batch Card. Two changes at once hide which one helped.

Sources

  1. Oregon State University Extension: Sauerkraut problems and solutions (SP 50-745)Soft kraut from too little salt (below 1.7%), uneven salting, high temperature or air pockets; slimy kraut is discarded; rotten surface layers are removed; discard if large amounts of mould are visible. Accessed 2026-10-09.
  2. NC State Extension: Pickle and pickle product problemsSlimy and mouldy pickles and pink kraut are unsafe; a white film of yeast on the brine surface is not harmful; too much salt, over 2.25%, can cause pink kraut. Accessed 2026-10-09.
  3. USDA Complete Guide to Home Canning, Guide 6: Fermented foods and pickled vegetablesTop-up brine of 1½ tablespoons salt per quart of water, boiled and cooled; canning or pickling salt; jars are acceptable but give more spoilage losses; a brine-filled food-grade bag as weight; discard pickles that turn soft, slimy or smell disagreeable. Accessed 2026-10-09.
  4. National Center for Home Food Preservation: Sauerkraut5 lb cabbage to 3 tablespoons canning or pickling salt; pack until juices cover; keep 1–2 inches under brine; 3–4 weeks at 70–75 °F (21–24 °C), 5–6 weeks at 60–65 °F (16–18 °C), may not ferment below 60 °F and may soften above 75 °F; remove scum 2–3 times a week; done when bubbling stops; keeps several months refrigerated. Accessed 2026-10-09.
  5. Clemson Cooperative Extension HGIC: Want to ferment vegetables? Start with sauerkrautFinal salt concentration of 2.25–2.5%; proper fermentation lowers the pH to 4.6 or below; do not use aluminium, copper, brass, galvanised or iron containers. Accessed 2026-10-09.

Numbers on this page come from these sources. Where sources give a range, we quote the range rather than a single figure.

A new, independently written guide at the address previously used for “How To Avoid Moldy Ferments & Other Dangers”.

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