Actually very easy

Sauerkraut

The beliefSauerkraut is assumed to be made with vinegar and lots of salt, and fermentation to be dangerous and uncontrolled.

The truthSauerkraut is made from cabbage and salt at 2% of the cabbage’s weight, nothing else. The cabbage’s own bacteria make the acid.

3–4 weeks

How to make it

What you need

1 kg white cabbage
20 g non-iodised rock salt (2% of the cabbage)
1 teaspoon of caraway or mustard seed, optional
A 1-litre wide-mouthed jar and a weight that fits inside

How the engine read this list (3 lines)

1000 g	White cabbage	cabbage
20 g	Non-iodised rock salt	salt
3 g	Caraway or mustard seed optional	mustard-seed

An empty weight means that line could not be turned into grams — either the amount is open ("to taste") or the ingredient has no record here. Neither enters the sum as zero; they do not enter it at all.

Set aside two of the outer leaves. Quarter the rest, cut out the core and slice it 2–3 mm thin.
Weigh the sliced cabbage and add salt at 2% of its weight (20 g per kilo).
Rub and squeeze it with your hands for 5–10 minutes, until the cabbage softens and liquid pools in the bowl.
Pack it into the jar a handful at a time, pressing hard each time, until its own liquid rises above it. Cover with the saved leaves and put the weight on top.
Close the lid loosely and leave it 3–4 weeks at 18–22 °C out of the sun. For the first week press it down every day to release the gas.
When it is sour enough for you, close the lid tightly and move it to the fridge.

Why it works

Cabbage leaves are covered in lactic acid bacteria; there is no need to add any. Salt is a selective filter for them: salt at 2–2.5% of the cabbage’s weight slows most spoilage bacteria while leaving the lactic acid bacteria working. The salt also pulls water from the leaves, and within a few hours the cabbage is sitting in its own brine. Fermentation is a relay. In the first days Leuconostoc mesenteroides dominates, making gas and a gentle acid, and the pH falls from 6 to below 4.5. As the acid rises, tougher species such as Lactobacillus plantarum take over and bring the pH to around 3.5. Temperature sets the pace: 3–4 weeks at 18–22 °C; above 24 °C it goes soft and over-sour, below 15 °C it takes months. One rule is absolute: the cabbage stays under the brine. At a surface that meets the air, mould works instead of lactic bacteria. In the US Food and Drug Administration’s definition, a food at pH 4.6 or below is in the acid class; that is the line that makes a pickle safe.

The rough sum

1020 grams going in

250 kcal in total

100% of the mass has figures behind it. This is the sum of what GOES IN rather than of what comes out. Wherever something evaporates, drains or ferments the two differ: a kilo of milk is 150 g of cheese.

Diets it qualifies for

Gluten-free Vegan Vegetarian Lactose-free

Storage & shelf life

How long it keeps

Fridge, under its own brine: 6 months
Room temperature, after fermentation: Not advised: it keeps souring and softening
Freezer: Not advised: it loses its crunch

What keeps sauerkraut is the lactic acid its fermentation makes. Finished kraut sits around pH 3.5, comfortably below 4.6, the low-acid line. The fridge protects it from over-souring more than from spoiling: at 4 °C the bacteria all but stop and the cabbage tastes the same for months.

When to bin it Pink colour, slimy or mushy cabbage, a rotten smell, or mould that has reached below the brine: throw all of it away. A thin white film on the surface (kahm yeast) is harmless: lift it off, and if the cabbage beneath stayed under the brine it is sound.

History

Where it comes from

Fermented cabbage was a source of vitamin C through the months without fresh vegetables across a wide belt from China to Central Europe. The German Sauerkraut means “sour herb”. In the eighteenth century James Cook had barrels of it loaded for his long voyages and made his crew eat it regularly. On the Black Sea coast, above all in Rize and Trabzon, fried pickled cabbage and pickle soup are winter staples, and collard greens are pickled the same way.

The knack

If the cabbage is still above the liquid the next day, top it up with 2% brine: 20 g salt per litre of water.
pH strips are cheap: before it goes into the fridge, check that it reads below 4.6, ideally 3.5–4.
Iodised salt does not stop the ferment but can cloud the brine and darken the colour; use rock salt.

Fermentation