Fermenting: Sauerkraut and Vegetables With Nothing But Salt and Patience

Fermenting is the oldest pantry in the world. No electricity, no canning kettle, no freezer. Just salt, vegetables and time. When the white cabbage stands heavy and dense in the bed in autumn, one head and two spoonfuls of salt turn into a jar of sauerkraut that carries you through the whole winter. And the best part: you do almost nothing. The real work is done by bacteria that were here long before you.

This article shows you the basic principle that every vegetable ferment follows. Once you can make sauerkraut, you can also do cucumbers, carrots, beetroot and beans: always the same story, under the brine, wait, taste.

What actually happens in the jar

Every cabbage leaf, every carrot, every cucumber naturally carries lactic acid bacteria. You do not need to add anything or buy a starter culture. These bacteria love two things: no oxygen and a little salt. That is exactly the environment you recreate in the jar.

As soon as the vegetables lie under the brine and the air is shut out, the lactic acid bacteria get going. They turn the sugar in the vegetables into lactic acid. This acid gives the finely tart taste, and it lowers the pH so far that rot and mould microbes no longer stand a chance. The vegetables preserve themselves. All you do is create the conditions, as long as you keep one single rule: everything stays under the brine.

Just salt and patience: the two percent rule

The whole craft stands or falls with the right amount of salt. Too little salt and the batch turns mushy or goes off. Too much, and the lactic acid bacteria themselves never get going. The sweet spot is two percent salt, based on the weight of the vegetables.

You can work it out in ten seconds: weigh the cleaned vegetables, one kilo takes 20 grams of salt, 500 grams takes 10 grams. A kitchen scale accurate to the gram is the only tool that really matters. Guessing by eye is not enough here.

White cabbage into sauerkraut: step by step

Brassica oleracea var. capitata, our white cabbage, is the classic way in. A firm storage cabbage like White Cabbage 'Dauerweiß' or 'Türkis' brings the dense leaves that turn juicy once you salt them.

1. Prepare the cabbage

   Take off the outer, wilted leaves, but set one or two nice ones aside. Quarter the head, cut out the hard core. Then shave or slice the quarters into fine strips, the thinner they are, the better the juice draws out later.

2. Salt and knead

   Weigh the cut cabbage, weigh out two percent salt and scatter it over. Now knead and pound firmly, five to ten minutes. The cabbage collapses, turns glassy and gives up its juice. This liquid is your brine, you do not need to add any water.

3. Layer into the jar

   Press the cabbage firmly into a clean jar or crock, handful by handful, until the brine stands above the cabbage. Leave no air pockets. Keep two to three centimetres free at the top, the kraut rises as it ferments.

4. Weigh it under the brine

   Lay a reserved cabbage leaf over the surface and hold it down with a weight: a clean jar filled with water, a fermentation stone, a small plate. Everything has to disappear under the liquid.

5. Let it ferment

   Cover loosely, do not seal airtight, fermentation gas forms and has to escape. At room temperature, ferment for seven to ten days. Then move it somewhere cool and let it keep maturing. From day ten you may start tasting.

Everything under the brine: the one principle

If you remember only one sentence from this article, let it be this: whatever the brine covers is safe, whatever sticks out of the brine is at risk. At the border between liquid and air, yeasts and mould settle in; in the sour interior they do not. That is why the weight matters so much. The cabbage wants to float up as it ferments, a good weight holds everything down. Check briefly every day for the first few days: is the brine still standing above the vegetables? If not, press it back down or top up with a two percent salt solution (20 grams of salt to 1 litre of water).

Kahm yeast versus mould: know the difference

After a few days a whitish film can form on top. Most of the time this is kahm yeast, and that is harmless: a thin, wrinkled, white skin on the brine, often slightly greyish. It smells yeasty, not rotten. Just skim it off with a clean spoon, the ferment beneath it is fine.

Mould, on the other hand, is something else and you will spot it easily: it grows furry and raised, in islands, and it is coloured. Green, blue, black, pink or fluffy white with visible threads. Mould smells musty and stale. Kahm yeast is a flat coating, mould is furry spots.

What else works: cucumbers, carrots, beetroot, beans

Once you have understood sauerkraut, the whole vegetable garden opens up. There are two ways: salt the vegetables and let them draw their own juice as with the cabbage, or lay firm vegetables into a ready-made two percent salt brine.

When to ferment: CW 38 to 46

The classic kraut season falls in autumn, when the storage cabbage is firm and heavy and the nights turn cooler: roughly CW 38 to 46, that is mid September to mid November. Cabbage that has caught a first light frost often tastes even milder and sweeter, because it converts starch into sugar.

Autumn is practical for another reason too: the home is no longer high-summer hot. The ideal is 18 to 22 degrees for the first fermentation phase. In heat above 25 degrees the fermentation runs too fast and turns mushy easily; in a cold larder below 15 degrees it takes a very long time instead. Autumn hits the temperature on its own.

Ripe, and then? Store it cool

When is it done? When it tastes right to you. After seven to ten days at room temperature, sauerkraut is young, crisp and mildly tart. Let it mature somewhere cool for another three to six weeks and it grows rounder and deeper. Taste your way through it every few days with a clean spoon, and once the flavour is where you want it, the jar goes into the fridge or a cool cellar at around 4 to 8 degrees. Cold slows the fermentation almost to zero, so finished sauerkraut keeps for many months, often well into the next year. One thing stays important even in the cold: the kraut stands under its brine.

Fermented vegetables are thereby a real pillar of your stores alongside the other autumn methods. Combine it with classic canning and preserving for compote and soups, and with storing in the cellar, sand box and clamp for root vegetables and whole cabbage heads. Together they fill your pantry until spring.

Häufige Fragen

How much salt do I need for fermenting?

The reliable rule of thumb is two percent salt, based on the weight of the cleaned vegetables. One kilo takes 20 grams of salt, 500 grams takes 10 grams. Weigh both with a kitchen scale accurate to the gram, guessing by eye is too imprecise. For a plain salt brine (for cucumbers or carrots, say) you dissolve 20 grams of salt in one litre of water. Use pure salt without anti-caking agents and without iodine.

Is the white coating on my sauerkraut mould?

Most likely not. A flat, wrinkled, white to slightly greyish film on the brine is kahm yeast and harmless. It smells yeasty and can be skimmed off with a clean spoon, the ferment beneath it is fine. Real mould, by contrast, grows furry and raised, in coloured islands (green, blue, black, pink) and smells stale. With real mould you throw out the entire batch, not just the spot.

Why does the vegetable have to stay under the brine?

Because lactic acid bacteria only work without oxygen, and the brine shuts out the air. Everything covered by liquid turns sour through the lactic acid that forms, and thereby keeps. Whatever sticks out of the brine gets air contact, and that is exactly where yeasts and mould settle in. A weight that holds the vegetables down is therefore the most important aid when fermenting.

When is the best time to make sauerkraut?

Autumn, roughly CW 38 to 46, that is mid September to mid November. That is when the storage cabbage is firm and ripe, and room temperatures at 18 to 22 degrees sit in the ideal range for the first fermentation phase. Summer heat above 25 degrees makes the batch turn mushy fast, a cold larder below 15 degrees slows the fermentation right down. A light frost in the field does the cabbage no harm, it even makes it sweeter.

How long does sauerkraut need to ferment and how long does it keep?

Reckon on seven to ten days at room temperature for the active fermentation phase, then the kraut is young and mild. If you like it rounder, let it mature somewhere cool for another three to six weeks. Taste your way through every few days with a clean spoon and put the jar in the fridge as soon as the flavour is right. Kept cool at 4 to 8 degrees and still under brine, sauerkraut keeps for many months, often into the next year.