Making sauerkraut is one of the easiest things you can do in the kitchen. All you need is cabbage, salt, and a jar. But how much salt? How long does it take? And why does a white film sometimes appear on the surface? In this article you will learn how cabbage fermentation works, what to look out for, and at the end you will find a tried-and-tested recipe for making your own sauerkraut.

Salt is the most important ingredient after the cabbage itself, but not because it does the preserving. The acid does the actual preservation work. Salt gives the lactic acid bacteria a head start: they tolerate salt better than most other micro-organisms. By adding the right amount of salt, the unwanted guests (yeasts, moulds, spoilage and pathogenic bacteria) are suppressed, allowing the lactic acid bacteria to do their work undisturbed.

The right amount is 2%, or 20 grams per kilogram of cabbage. That number is not arbitrary: below 2%, the inhibition is insufficient and yeasts and other bacteria get their chance, leading to mushy textures, off-flavours, and sometimes genuinely dangerous situations. Above 3%, you also inhibit the lactic acid bacteria themselves, fermentation stalls, and the result is simply too salty.

Always weigh your salt. Eyeballing it will go wrong sooner or later.

WHAT KIND OF SALT SHOULD I USE FOR SAUERKRAUT?

You can use any type of salt for making sauerkraut. You will read everywhere that you must use non-iodised sea salt. The idea is that iodine has an antibacterial effect and disrupts fermentation. In practice, the amount of iodine in regular table salt is so small that the effect is negligible. Use non-iodised salt if you have it, but there is no need to worry about it.

WHEN SHOULD YOU USE A STARTER CULTURE?

For regular sauerkraut, you do not need a starter. The bacteria are already on your cabbage. But there are situations where a vegetable fermentation starter culture is useful: when you want to ferment cooked vegetables, when working with sugar-rich vegetables or fruit, or when you want a more consistent and predictable fermentation. The starter introduces a broad range of lactic acid bacteria at once, which speeds up the process and reduces the chance of off-flavours.

Lactic acid bacteria work at virtually any temperature above freezing, but the temperature determines the character of your end product.

At 18–21°C (room temperature), fermentation takes two to three weeks. This is the most common method and gives good results.

Below 10°C, for example in a cellar or cool storage room, fermentation is much slower: six to eight weeks or longer. The result is more complex and fuller in flavour, because the bacteria that are active at low temperatures produce different and more flavour compounds. If you have a cool space available, give it a try.

Above 25°C, fermentation proceeds quickly, but the flavour becomes flatter and the texture softer. Never place your sauerkraut in direct sunlight or near heat sources.

At room temperature, your sauerkraut will be ready in two to three weeks. At cooler temperatures, it can take six to eight weeks.

You know it is done when it tastes good (this is always the primary criterion), when gas production has stopped or nearly stopped, when the pH is below 4.6 (if you want to measure it), and when at least two weeks have passed at room temperature.

After that, put the sauerkraut in the fridge. This virtually stops fermentation. In the fridge, sauerkraut keeps for months, as long as the cabbage stays submerged in brine. Always keep the brine.

Ingredients (for approx. 750 grams of sauerkraut):

Equipment:

1. Remove the outer leaves of the cabbage. Set one clean leaf aside.
2. Cut the cabbage in half, remove the hard core, and slice it as thinly as possible into strips.
3. Weigh the sliced cabbage and weigh out 2% of that weight in salt (20 grams per kilo).
4. Mix salt and cabbage in a large bowl. Then pound, squeeze, and knead the cabbage for five to ten minutes until it turns glassy and releases plenty of liquid. Let it rest briefly and repeat.
5. Add spices if desired and mix through.
6. Pack the cabbage into the jar layer by layer, pressing down firmly after each layer. The cabbage must be fully submerged in its own brine.
7. Cover with the reserved cabbage leaf or place something heavy on top (a weight stone, a bag filled with brine).
8. Sluit af met een airlock of deksel en zet de pot donker weg bij kamertemperatuur (18–21°C).
9. Check during the first few days that the cabbage remains submerged. Skim off any kahm yeast.
10. Taste after two weeks. Sour enough for your liking? Optionally measure the pH: it should be below 4.6 (usually around 3.5). Move to the fridge.

Variations
• Pointed cabbage: see above. Pointed cabbage is an excellent choice for beginners.
• Wine sauerkraut: add 50 ml dry white wine per kilogram of cabbage after fermentation is complete.
• Pink sauerkraut: mix a small amount of red cabbage through the white cabbage.
• Pointed cabbage with spices: pointed cabbage with fennel seed and orange zest is a surprising combination.

Want to go deeper? Over Rot (in Dutch) covers everything about the microbiology of vegetable fermentation, including a full chapter on sauerkraut and all its variations. Prefer video? Our online vegetable fermentation course teaches you sauerkraut, kimchi, and pickles in 25 bite-sized video lessons.