How to Make Sauerkraut: A UK Beginner's Guide

What actually is sauerkraut?

Sauerkraut is finely shredded cabbage that has soured through lacto-fermentation. There is no vinegar involved, and that is the part most people find surprising. You do not add acid to sauerkraut. The cabbage makes its own.

Raw cabbage carries harmless lactic acid bacteria on its leaves. Give them salt, no oxygen and a little time, and they get to work on the natural sugars in the cabbage, converting them into lactic acid. That acid is what makes sauerkraut tangy, keeps it preserved and gives it the living, gut-friendly quality people prize. The vegetables ferment themselves.

This is the key difference from a jar of shop pickled cabbage. Quick pickling works by steeping vegetables in vinegar you have added, so the sourness comes from outside. Fermenting builds the sourness from within. If you want the full contrast between the two methods, our guide to pickling vegetables walks through the vinegar route. For the wider principles behind souring any vegetable this way, start with our primer on fermenting vegetables.

You do not add acid to sauerkraut. The cabbage makes its own.

Why does salt matter so much?

Salt does three jobs, and all three matter.

First, it pulls water out of the cabbage. As the salt draws moisture from the shredded leaves, that liquid becomes the brine the cabbage will sit under. You are not adding water to sauerkraut either. The cabbage provides it.

Second, salt sets the conditions. At the right concentration it holds back spoilage organisms while the lactic acid bacteria you want are perfectly happy to carry on. That head start matters most in the first day or two, before the acid has built up.

Third, salt keeps the finished kraut crisp rather than mushy.

The reliable ratio is about 2% salt by the weight of your prepared cabbage. Colorado State University Extension recommends 2 to 2.5% salt by weight, roughly 3 tablespoons per 5 pounds of shredded cabbage. In metric terms that 2% works out at about 20g of salt per 1kg of cabbage.

The important part: weigh it, do not guess. Salt crystals vary enormously in size, so a tablespoon of flaky salt and a tablespoon of fine salt hold very different amounts. Put your mixing bowl on kitchen scales, zero it, add the shredded cabbage and note the weight, then measure out 2% of that number in salt. A 900g cabbage needs about 18g of salt. Use non-iodised salt where you can, because the iodine in table salt can interfere with the fermentation.

The method, step by step

You need one medium cabbage, non-iodised salt, kitchen scales, a large bowl, a clean glass jar (a 1 litre Kilner-style jar is ideal) and something to weigh the cabbage down.

1. 1

   Shred the cabbage

   Peel off the outer leaves and keep one aside. Quarter the cabbage, cut out the hard core, then shred the rest as finely as you can with a sharp knife, a mandolin or a food processor. Finer shreds release their liquid more easily.

2. 2

   Weigh and salt

   Put the shredded cabbage in your bowl on the scales and note the weight. Measure out 2% of that weight in salt, about 20g per 1kg, and scatter it through the cabbage.

3. 3

   Massage until it releases liquid

   Scrunch and squeeze the salted cabbage with clean hands for 5 to 10 minutes. It will soften, wilt and start to pool with brine at the bottom of the bowl. Keep going until you can grab a handful and squeeze liquid out of it easily.

4. 4

   Pack it tight

   Press the cabbage firmly into your jar a handful at a time, pushing down hard to knock out air pockets. The brine should rise up and cover the cabbage. Pour in any liquid left in the bowl. Leave a few centimetres of space at the top.

5. 5

   Submerge and weight it down

   Fold the reserved outer leaf and tuck it over the top to hold stray shreds down, then add a fermentation weight, a small clean glass jar or a brine-filled food bag to keep everything below the liquid. The cabbage must sit under at least a centimetre or so of brine.

6. 6

   Cover loosely

   Rest the lid on top without sealing it tight, or use a fermentation airlock. The fermentation produces carbon dioxide that needs to escape, so a fully sealed jar can build up pressure. Stand the jar on a plate to catch any brine that bubbles over.

If the cabbage does not make quite enough brine to cover itself after packing, top it up with a little extra brine made from 20g of salt dissolved in 1 litre of cooled boiled water. Never top up with plain water, which dilutes the salt and weakens your protection.

How long, and at what temperature?

Sauerkraut ferments at room temperature, and a normal UK kitchen at around 18 to 22°C is well within the sweet spot. Colorado State University Extension puts the ideal range at roughly 20 to 22°C (68 to 72°F) for about 7 to 14 days. The National Center for Home Food Preservation notes that at 21 to 24°C (70 to 75°F), kraut is fully fermented in about 3 to 4 weeks. So expect anywhere from 1 to 4 weeks depending on your kitchen. Warmer speeds it up, cooler slows it down.

Taste is your guide, not the calendar. Start sampling after about 5 to 7 days, using a clean fork and pressing the cabbage back under the brine afterwards. It will begin mild and salty and grow steadily more sour and complex. When it tastes right to you, move the jar to the fridge. The cold does not stop the fermentation but slows it to a crawl, holding the flavour roughly where you like it. The Food Standards Agency advises keeping your fridge between 0 and 5°C, which is exactly where finished sauerkraut is happiest for long keeping.

How do I know it is working, and when should I bin it?

A healthy ferment gives you clear, reassuring signals in the first few days:

• Small bubbles rising through the jar, especially when you tap it.
• A fresh, sour, cabbagey smell, tangy rather than unpleasant.
• Brine that turns slightly cloudy, which is the lactic acid bacteria multiplying as they should.

None of that is cause for concern. It is the sign your cabbage is souring properly.

The signs to stop and throw a batch away are different and worth knowing before you start:

• Fuzzy mould of any colour on the surface, particularly on cabbage that has floated above the brine. FermentWorks, a fermentation authority, is blunt about mould: it is something you do not want to eat, so compost the batch.
• A slimy, ropey or stringy texture running through the cabbage.
• A genuinely putrid, rotten or foul smell, quite distinct from the pleasant sourness of a good ferment.

Kahm yeast is the one that trips beginners up, because a flat white film looks alarming. It is not mould. It appears as a thin, matte, sometimes wrinkled skin across the surface, it has no fuzz, and it breaks up and scatters when you poke it. It is harmless, though it can add a slightly yeasty off-note if left. Skim it off with a clean spoon and press the cabbage back under. If it keeps returning, move the jar to the fridge. When in doubt, trust your senses together: colour, texture and smell will tell you if something is truly wrong.

Flavour variations to try

Plain salted cabbage is the classic, and once you have made it once you can start playing. Add these at the salting stage so they ferment along with the cabbage:

• Caraway seeds. The traditional partner for sauerkraut, warm and faintly aniseed. A teaspoon or two per cabbage.
• Juniper berries. Lightly crushed, they bring a resinous, gin-like note that suits richer meals.
• Grated carrot. A big handful adds colour, a touch of natural sweetness and a softer edge. Apple, shredded beetroot, a little grated ginger or a pinch of dill all work the same way.

Keep the additions modest on your first few batches so you can taste what each one does. The cabbage and salt do the real work. Everything else is seasoning.

Making sauerkraut is one of the most forgiving things you can ferment. Get the salt right, keep it under the brine, and give it time. A single cabbage and a spoonful of salt turn into jars of something tangy, keeping and alive, for almost no money and very little effort.