Can You Make Sauerkraut With Red Cabbage?
Yes, and it turns a remarkable magenta. Red cabbage is firmer, takes longer and needs more work to release its brine. Here is what changes, what stays the same, and how to get the colour right.
Yes. Red cabbage ferments perfectly well, and it produces the best-looking thing that will ever come out of your kitchen — a deep magenta kraut with brine the colour of blackcurrant cordial.
The process is the same as green. Three things behave differently: it is firmer and harder to work, it takes longer, and the colour does something interesting that is worth understanding.
Why it turns bright pink
Red cabbage gets its colour from anthocyanins, the same family of pigments that colour blackberries, blackcurrants and red wine.
Anthocyanins change colour with pH. They are one of the classic natural indicators, and schoolchildren have used red cabbage water to test acids and alkalis for generations.
In alkaline conditions they go blue, then green, then yellow. Neutral, they are purple. In acid, they go bright pinkish-red.
Fermentation produces lactic acid, so the pH falls steadily from around 6 down to about 3.4. The cabbage follows the pH down, moving from dull purple to vivid magenta as it sours.
This is genuinely useful. The colour is a rough progress indicator. A jar that has gone properly bright is a jar that has become properly acidic, and a jar still looking dull purple after a fortnight has not got going.
The brine goes the same colour, only more so. It is a startling deep pink and it is worth keeping for that reason alone — a splash turns a dressing an unlikely shade.
What is different about red cabbage
It is firmer
Red cabbage has thicker, denser leaves and a stiffer structure than most green varieties. The heads are usually tighter.
The practical consequence is that it does not give up its water easily. Where a green cabbage releases enough brine after five minutes of squeezing, red can take ten or fifteen, and you have to mean it.
Shred it finer than you would green cabbage. More cut surface means more water released, and it makes the squeezing far less of a battle.
It takes longer
Expect four to six weeks rather than three, at the same temperature. The denser tissue takes longer for the acid to work through.
It also stays crunchier at the end. Red cabbage kraut that has fermented for six weeks is still firmer than green kraut at three, which many people prefer.
It stains everything
Hands, chopping boards, plastic containers, tea towels, worktops. Anthocyanins are strong dyes.
Hands come clean in a day. Plastic does not — a plastic tub used for red cabbage stays pink for life. Wooden boards will take a stain too. Use glass or stainless steel for the mixing if you mind, and expect any plastic vessel to be permanently marked.
It tastes different
Peppery and slightly more mineral than green kraut, with a faint bitterness underneath. Some people prefer it and some do not.
It suits richer additions better than green does. Apple, juniper and caraway all work particularly well with it.
How to make it
Weigh the cabbage after shredding. Remove the outer leaves and the core, quarter it, and shred it as finely as you can manage. Weigh what you have.
Salt at two per cent. Twenty grams of salt per kilogram of shredded cabbage. Weigh it — do not measure by spoon. Use salt without iodine or anti-caking agents.
Squeeze, and keep squeezing. Massage the salt in and work it hard. With red cabbage this takes ten to fifteen minutes. The cabbage will go from dry and springy to wet and limp, and a pool of purple liquid will collect at the bottom of the bowl.
If your hands give out, salt it and leave it for half an hour, then come back. The salt will have done some of the work by osmosis and the second round is easier.
Pack it down hard. Into a jar or a bucket, pressing firmly as you go so the brine rises above the cabbage. Leave a fifth of the container empty.
Weigh it under. Everything must stay below the brine. A small jar inside the big one, a brine-filled bag, or a proper glass weight.
Cover loosely so gas can escape, and leave it somewhere around 18 to 20°C out of direct sunlight.
Wait four to six weeks, tasting from about week three. When the colour is bright and the taste is right, move it somewhere cold.
If it does not release enough liquid
The most common red cabbage problem, and it happens because the cabbage was older, drier or not shredded finely enough.
Do not just add water. Make brine at the same strength — twenty grams of salt per litre — and top up until the cabbage is covered. Adding plain water dilutes the salt below the level that protects the ferment.
Prevention: shred finer, squeeze longer, and use the freshest cabbage you can get. A cabbage that has sat in a shop for a fortnight has already lost water and will not give up much more.
If it goes blue or grey
Disconcerting, and usually harmless.
Anthocyanins go blue in alkaline conditions. If your tap water is hard and alkaline, the first day or two can look blue or greyish rather than purple. As the acid builds, the colour swings back to red.
If it is still blue or grey after a week, the ferment is not acidifying. That is the real problem, and the colour is only telling you about it. Check the temperature is warm enough, check the salt was not overdone, and check whether there is any bubbling at all.
Using filtered or boiled-and-cooled water for any brine you add avoids the alkalinity problem, and also removes chlorine, which inhibits the bacteria you want.
Is it better for you than green?
Slightly, and mostly because of the pigment.
Anthocyanins are antioxidants and are the subject of a considerable amount of research. Red cabbage contains a great deal of them and green contains almost none. Fermenting preserves them — unlike boiling, which leaches them straight into the water and turns it blue.
Red cabbage also carries more vitamin C than most green varieties, and fermenting preserves vitamin C well.
Everything else is much the same: fibre, vitamin K, the isothiocyanates that all brassicas produce, and the live bacteria that any vegetable ferment gives you.
The difference is real but modest. Make it because it looks extraordinary and tastes good, not because it is a different category of food.
Things worth adding
Red cabbage takes strong flavours better than green.
Apple. Grated in at about one part apple to six parts cabbage. It adds sweetness and sugars for the bacteria, and it is the classic pairing.
Juniper berries. A dozen crushed berries per kilogram. Resinous and excellent with red cabbage.
Caraway seeds. A teaspoon per kilogram. The traditional sauerkraut spice, and it is also said to reduce the digestive effects of eating a lot of cabbage.
Beetroot. Grated in, it deepens the colour further and adds earthiness. It also adds sugar, so the ferment moves faster.
Ginger. A thumb, grated, per kilogram. Sharpens the whole thing.
Onion or garlic. Both work. Garlic can turn blue-green in an acidic ferment, which is a harmless reaction between sulphur compounds and trace copper, and alarms people every time.
Keep additions to no more than about a fifth of the total by weight. Cabbage is what makes the brine, and diluting it too far leaves you short of liquid.
Mixing red and green
You can, and it works, but the colour wins. Anthocyanins bleed into everything, so a jar of half and half comes out uniformly pink rather than striped.
Practically, mixing is useful when you have more red than you want and some green to hand: the green shreds more easily and releases liquid faster, which helps the red get going.
If you want two colours on a plate, ferment them in separate jars.
Choosing the cabbage
The cabbage decides how easy the job is, and it matters more with red than green.
Look for a head that feels heavy for its size. Weight means water, and water means brine. A light head has already dried out and will fight you.
The outer leaves should be tight and squeaky rather than loose and papery. Cut surfaces on the stem should look fresh rather than dried and brown.
Freshly cut is best by a distance. Red cabbage stores well, which is a virtue in a vegetable rack and a problem in a fermenting bowl — a head that has been in storage for two months has lost a lot of water and will not give it up.
If you grow your own, this is one of the best arguments for doing so. A cabbage cut in the morning and shredded in the afternoon releases brine readily and needs far less squeezing. Red varieties are also among the easier brassicas to grow and stand well into winter.
Organic or unsprayed is worth having if you can, for a specific reason rather than a general one: the bacteria that do the fermenting live on the leaves, and you want them present and healthy. This is also why you do not wash the cabbage thoroughly before shredding.
Temperature and timing
Temperature does more to the result than almost anything else, and it is the easiest thing to control.
Around 18 to 20°C is the sweet spot. Fast enough to acidify promptly, slow enough to keep texture and build flavour.
Above 24°C and it moves quickly, but the texture softens and the flavour comes out flatter and less complex. A kitchen in summer is often too warm.
Below 15°C and it slows considerably. Not a problem, and arguably better — a cold, slow ferment produces the best flavour and the firmest texture. It simply takes two or three months rather than one.
Red cabbage tolerates the cool end well because it stays firm anyway. If you have a cold larder and patience, a slow winter ferment is the best version of this.
Keep it out of direct sunlight regardless. Light degrades the anthocyanins and you will lose some of the colour you went to the trouble of getting.
What to do with the brine
Do not pour it away. It is the most useful by-product in the kitchen and it is a startling colour.
In dressings. It is acidic enough to replace some or all of the vinegar, and it turns a vinaigrette bright pink.
As a starter. A few tablespoons added to a new batch of anything gives the bacteria a head start and gets it acidifying faster. Useful in cold weather or with a cabbage that seems reluctant.
In soup, stirred in at the end so the heat does not kill it.
Frozen in ice cube trays, which keeps it usable all year.
Drunk on its own, a small glass at a time. It is salty and sharp and an acquired habit, but it is a concentrated dose of everything the ferment produced.
Storage and serving
Once it tastes right, move it somewhere cold — a fridge, cellar or unheated larder. It will keep for six months or more with the cabbage still under the brine, and it stays crisp.
It carries on souring slowly in the cold, and the colour deepens further over the first few weeks of storage.
Serve it as a condiment rather than a vegetable. A forkful alongside something rich — pork, sausage, cheese, oily fish, a fatty roast — is what it is for. It is very good in a sandwich and better still with cold meat.
Do not cook it if you want the live bacteria. Heat above about 46°C kills them. If it is going into a hot dish, add it at the end.
Mistakes worth avoiding
Shredding it too coarsely. The single commonest reason red cabbage will not make enough brine.
Giving up on the squeezing too early. It takes twice as long as green. Salt it and walk away for half an hour if your hands are tired.
Topping up with plain water. Always brine at the same strength.
Judging it at three weeks. Red cabbage is slower. Give it four to six.
Using a plastic container you care about. It will be pink forever.
Panicking at a blue tinge on day one. Give it a week before worrying.
The short version
Red cabbage sauerkraut works exactly like green, with three differences: shred it finer, squeeze it twice as long, and give it four to six weeks instead of three.
The colour shifts from dull purple to bright magenta as the acid builds, which is a useful rough guide to progress. Everything must stay under the brine, and any topping up is done with brine, never water.
It will stain any plastic you put it in permanently, so use glass if you mind.
