How to make sauerkraut at home: salt ratio, packing, timing and spoilage signs

TUREFF• •0

Sauerkraut is the classic first ferment: one cabbage, a spoonful or two of salt, and a few weeks of patience. Done well it is crisp, sour and keeps for months in the fridge. This guide walks through the method that university extension services use, and how to tell a harmless surface film from a batch that has gone wrong.

What you need

One firm head of white or green cabbage (red cabbage works too and turns everything pink)
Non-iodised salt
Kitchen scales
A clean glass jar or food-safe crock
A weight that fits inside the jar
Optional: caraway seeds, juniper berries or grated carrot

The salt ratio

Extension guides give about 2.25 to 2.5 per cent salt by weight for sauerkraut. Weigh the cabbage after you have shredded it and multiply:

1 kg cabbage = about 23 to 25 g salt
2 kg cabbage = about 45 to 50 g salt

Weighing matters. Too little salt and the cabbage can soften or spoil before enough acid forms. Too much, or salt spread unevenly, and the kraut can turn pink, ferment sluggishly or encourage surface yeasts. Use iodine-free salt, because iodine can hold back the bacteria you need.

Method

Prepare. Remove the outer leaves and keep one or two clean ones aside. Quarter the cabbage, cut out the core and shred it thinly with a knife or mandoline.
Salt. Put the shredded cabbage in a large bowl, sprinkle the salt over it and mix thoroughly so every strand is coated.
Massage. Squeeze and scrunch the cabbage with clean hands for several minutes. It will soften, shrink and start to release liquid. Leave it to sit for 10 to 20 minutes and massage again.
Pack. Push handfuls into the jar, pressing each layer down hard with your fist or a wooden tamper so the brine rises and the air pockets disappear.
Cover with brine. By the time the jar is full, the cabbage should be under its own liquid. If it is not after an hour or two, top up with a little 2 per cent brine (about 20 g salt per litre of water).
Weigh down. Tuck one of the reserved outer leaves over the top, then add the weight so nothing floats above the brine.
Cover loosely with a lid that lets gas escape, a cloth, or an airlock lid, and stand the jar on a plate.

Temperature and time

Extension guidance suggests a temperature of roughly 20 to 24 degrees C (around 68 to 75 F). At that temperature, fermentation is usually complete in about 3 to 4 weeks. Cooler rooms take longer and give a more complex flavour; warmer rooms speed things up but make a softer kraut and invite mould. Start tasting after a week or so. When it is as sour as you like, close the jar and refrigerate it.

Daily checks

Press the cabbage down so it stays under the brine.
Top up with brine of the same strength if the level falls.
Expect bubbles, cloudiness and a sour smell, especially in the first week.

Kahm yeast versus mould

Kahm yeast is a flat, thin, white or cream film on the surface of the brine. It can look wrinkled and smell a little odd, but it is not harmful. It tends to appear when there is too much air, too little acid early on, or a warm room. Skim it off, check the kraut below smells sour and clean, and make sure everything is submerged. Extension guides also advise removing any discoloured kraut in the top layer. Mould is raised and fuzzy, often in round spots, and may be green, blue, black or pink. Because mould can send threads down into the food beneath, the safest course is to discard the whole batch.

Other signs it has gone wrong

Slimy or very soft kraut
A rotten, putrid smell instead of a clean sour one
Dark brown or pink discolouration throughout, not just at the surface

Any of these mean the batch should go. When in doubt, throw it out.

Storing and using

Kept cold and under its brine, sauerkraut lasts for months, slowly getting more sour. Always use a clean utensil. Heating it kills the live bacteria, so add it to dishes at the end if you want to keep them. How long do you ferment yours, and what do you add? Share your tips or ask about a problem batch in the comments.