Homemade sauerkraut: the workshop, step by step

Homemade sauerkraut is two ingredients and a kitchen scale: shredded cabbage, and salt at 2 per cent of its weight, packed under its own juice somewhere between 21 and 24 °C. Everything else, the clamp-lid jars, the glass weights, the recipes that measure salt by the handful, orbits around that one weighing. If you take away a single thing, take away the percentage, and the fact that it is calculated on the shredded cabbage rather than on the whole head.

Three corrections before you start, because each of them runs against what most recipes say. Iodised salt does not stall the fermentation, and in Switzerland it is the salt to choose. Sauerkraut is not richer in vitamin C than the cabbage it came from; it is poorer. And its defining nutritional feature is neither a vitamin nor a probiotic. It is sodium: roughly 660 mg per 100 g in the USDA composition tables, which is about 1.7 g of salt in a small serving.

What lactic fermentation actually does

The bacteria that will transform the cabbage are already sitting on its leaves. Salt does not add them. It draws water out of the cells by osmosis, which creates the brine, and it slows the competing microbes enough for lactic acid bacteria to take over. Those bacteria feed on the sugars in the cabbage and produce lactic acid, a little acetic acid and carbon dioxide. The pH drops, and below about 4.0 the jar stops being a place where spoilage organisms or enteric pathogens can grow.

The bacterial succession is well documented. In an experiment published in Food Microbiology in 2018, a cabbage fermentation without a starter culture saw its lactic acid bacteria climb from around 10⁵ to 10⁹ colony-forming units per millilitre, with the pH falling below 4.0 only after three days. With a starter inoculated at roughly 10⁷ CFU/ml, the same threshold was reached within 24 hours. Sequencing showed that spontaneous fermentations carried a far more varied community in the first days, including enterobacteria and pseudomonads, later displaced by lactic acid bacteria.

That lag explains why duration matters as much as salt. The first three days of a spontaneous ferment are the window when the jar is not yet acidic and unwanted organisms are still around. A microbiological survey published in 2026 in the International Journal of Food Microbiology, covering 75 unpasteurised commercial fermented vegetables, tested the question head on: challenge tests on white cabbage showed that rapid acidification below pH 4.4, followed by a holding period of at least 14 days under good conditions, effectively limits pathogen survival and outgrowth. The same survey found no Salmonella, no Listeria monocytogenes and no E. coli in any of the 75 samples, but did find Enterobacteriaceae in six of them, the signature of ferments that never acidified properly.

Hold on to that number: fourteen days minimum, not one week. Tasting after seven days out of curiosity is harmless, but it is not the moment to move the jar to the fridge and call the job done.

Salt: 2 per cent, and why iodised salt is fine

The reference recipe from the National Center for Home Food Preservation, adapted from the USDA Complete Guide to Home Canning, gives 25 pounds of cabbage to three quarters of a cup of canning salt, which is about 11.3 kg to 220 g. That works out at roughly 2 per cent, and it scales down cleanly: 3 tablespoons of salt per 5 pounds of cabbage, or in the units that matter here, 20 g of salt per kilogram of shredded cabbage.

This range is not a matter of taste. Too little salt gives a weak brine, a soft texture, and a ferment where unwanted organisms keep their place for longer. Too much slows the lactic acid bacteria themselves, delays the pH drop, and leaves you with something hard and brackish. The troubleshooting table published by the NCHFP puts weak brine and excessive temperature at the very top of its list of causes for soft fermented vegetables.

The advice to avoid iodised salt appears in almost every fermentation recipe, and it has been tested. The 2018 Food Microbiology trial compared cabbage fermentations with and without 1 per cent iodised table salt, with and without starter cultures. Iodised salt had no statistically significant effect on the microbial populations, and iodine measurements showed that the fermentation did not change its concentration either. The authors conclude that there is no basis for the popular belief that iodised salt inhibits the bacteria responsible for sauerkraut fermentation.

In Switzerland this is not a neutral detail. According to the Federal Food Safety and Veterinary Office, iodised salt, both in the household and in processed foods, supplies 51 per cent of the population’s iodine intake, ahead of dairy products at 26 per cent and fish and seafood at 9 per cent. Swiss table salt now contains 25 mg of iodine per kilogram, up from 3.75 mg when the programme began. The office explicitly advises vegetarians and vegans to choose iodised salt, because many milk alternatives contain none. Swapping every gram of iodised salt for grey sea salt does nothing for your ferment and removes a source of iodine.

Fine non-iodised salt keeps one marginal advantage: it dissolves faster while you are massaging. That is a convenience, not a success factor.

Kit, stripped back

A kitchen scale that reads in grams. A knife or a mandoline. A large bowl. A fermentation vessel. A weight.

For the vessel, the NCHFP gives a useful ratio: about one gallon of container per five pounds of fresh vegetable, which makes a five-gallon stone crock the ideal size for 25 pounds of cabbage. Fermenting in quart or half-gallon Mason jars is described as an acceptable practice, but one that leads to more spoilage losses, because the ratio of exposed surface to volume works against you. At home, a 1.5 to 2 litre jar for a 1 to 1.2 kg cabbage is a sensible compromise.

The weight is the part that actually matters. Cabbage has to stay 1 to 2 inches below the brine for the whole fermentation, and that requires something pressing down. A glass weight, a small water-filled jar, a weighted plate: the object hardly matters, its ability to hold the mass under liquid matters a great deal. The whole cabbage leaf laid on top, often presented as the solution, is only a barrier layer. It floats like everything else if nothing holds it down.

A word on sterilising, which every recipe seems to demand. Boiling the jar for ten minutes before filling it with raw cabbage makes little sense in a spontaneous ferment, since the useful bacteria arrive with the cabbage and the glass is not a growth medium. Careful washing in hot soapy water, well rinsed, is enough. What counts is elsewhere: clean hands, a clean work surface, and a cabbage whose damaged outer leaves have gone.

The method, by weight

Choose and prepare. A white or green cabbage, firm and heavy for its size. The NCHFP recommends starting the kraut between 24 and 48 hours after harvest, which in practice means buying a cabbage that has not been sitting around and not leaving it a week in the fridge before you get to it. Strip the wilted outer leaves, quarter it, cut out the hard core.

Shred. Two to three millimetres. An even cut ferments evenly and gives a predictable texture; a very fine cut releases more juice but ends up softer.

Weigh, then salt. Weigh the shredded cabbage in the bowl, with the scale tared. Multiply by 0.02. For 1,100 g of cabbage that is 22 g of salt. That is the whole calculation.

Massage. Five to ten minutes, pressing properly. The juice should cover the cabbage when you push it down with your fist. If not enough juice appears, leave it fifteen minutes and come back to it; the salt needs time. As a last resort, top up with brine made separately, in the proportion the NCHFP gives: one and a half tablespoons of salt per quart of boiled, cooled water.

Pack. By handfuls, pressing firmly at each layer to drive out air pockets. Stop about 5 cm below the rim, because active fermentation raises the level and overfilled jars spill.

Weight and cover. Put the weight in. Check that every shred is under the juice. Cover without sealing airtight, or use a clamp lid you open regularly. The CO₂ has to get out. A screw-top jar closed tight and forgotten in a cupboard for three weeks is a pressure vessel.

Temperature and time, the part recipes skip

This is the parameter most often garbled. The USDA recommendation, carried by the NCHFP, is to store the vessel at 70 to 75 °F, that is 21 to 24 °C, while it ferments. In that range, kraut is fully fermented in about three to four weeks. At 60 to 65 °F, roughly 15 to 18 °C, it takes five to six weeks. Below 60 °F it may not ferment at all. Above 75 °F it tends to go soft.

The common instruction to start at room temperature and then move the jar somewhere cool, around 15 to 18 °C, therefore selects the slowest fermentation, with a longer initial acidification phase, which means a longer window of vulnerability. A simpler plan: leave the jar in a room at 20 to 22 °C from beginning to end, and move it to the fridge when the flavour suits you.

The end-point signs need no equipment. Bubbling stops. The liquid, cloudy at peak activity, clears. The taste turns properly sour without bitterness. If you have pH strips, a finished kraut usually lands between 3.4 and 3.8; the 2026 survey of commercial products recorded a range of 3.1 to 4.3 across 75 samples, which also tells you how variable spontaneous fermentation is.

Once cold, sauerkraut keeps for months. The NCHFP states that fully fermented kraut may be kept tightly covered in the refrigerator for several months, or canned, in which case the heat treatment kills the live bacteria.

What goes wrong, and what to throw away

A white film on the surface is the most common event. These are aerobic surface yeasts that feed on the acid and gradually weaken the protection the acidity provides. The NCHFP table is direct about the remedy: remove the scum as often as needed. It does not make the jar dangerous, but letting it build up degrades both flavour and acidity.

Actual mould, fuzzy and coloured green, black or pink, is a different matter. It means cabbage has been sitting in contact with air, and moulds push filaments into the matrix well beyond the visible patch. On a domestic jar, the sensible decision is to discard, not to scoop around it.

A soft, slippery texture points back to the two causes the NCHFP lists first: brine too weak, and fermentation temperature too high. Marked bitterness can come from a salt substitute, since potassium chloride, the main ingredient in most low-sodium salts, causes bitterness, which makes it a poor choice here.

A sharp, sour, slightly pungent smell is normal, especially in the early days. A putrid, rotting, bin-like smell is not, and it cannot be rescued.

Sodium, the figure nobody prints

Compare what the composition tables say. Per 100 g, raw white cabbage contains 18 mg of sodium, 36.6 mg of vitamin C, 76 µg of vitamin K, 2.5 g of fibre and 25 kcal (USDA SR Legacy, code 169975). Canned sauerkraut, solids and liquids, contains 661 mg of sodium, 14.7 mg of vitamin C, 13 µg of vitamin K, 2.9 g of fibre and 19 kcal (code 169279).

The ratios are hard to miss. Vitamin C is cut by a factor of two and a half, vitamin K by nearly six, and sodium is multiplied by thirty-seven. Those 661 mg of sodium correspond to about 1.7 g of salt. A 150 g serving therefore carries roughly 2.5 g of salt.

Set against Swiss benchmarks, that is not trivial. The national salt consumption study 2022-2023 run by the Federal Food Safety and Veterinary Office found that adults in Switzerland eat 8.7 g of salt a day on average, about 75 per cent above the 5 g recommended by the WHO, with 7.4 g among women and 9.9 g among men; only 14 per cent of the population stays under 5 g. The WHO recommends less than 2,000 mg of sodium a day, equivalent to less than 5 g of salt, and notes that global mean adult intake was 4,278 mg of sodium a day in 2021.

In other words, a generous plate of sauerkraut occupies half a daily salt budget that is already being overshot in Switzerland. That does not make it a food to avoid, but it does reframe the question. This is not a vegetable you eat by volume. It is a sour condiment you add by the spoonful. Rinsing sauerkraut in cold water before serving removes some of the surface salt, at the cost of some acidity and some live bacteria.

Potassium is the other half of the picture. The Swiss study puts average intake at 2.7 g a day, matching an excretion level that corresponds only just to the WHO minimum of 3.5 g, with women of all ages and men aged 18 to 29 falling below it. Vegetables, fruit, nuts, wholegrains and pulses are the main sources. Sauerkraut served with potatoes and pulses works in the right direction on that count.

Vitamins and probiotics: what the evidence supports

The claim that fermentation “increases the bioavailability of vitamins” is repeated everywhere. On vitamin C, the composition tables say the opposite: raw cabbage contains distinctly more. Washing, salting, time and air exposure all cost something. Sauerkraut remains a reasonable source of vitamin C against the adult requirement, which the NHS puts at 40 mg a day, but it is not better than the cabbage it came from.

On vitamin K, work published in npj Science of Food in 2026 adds an interesting wrinkle: a single 12-hour frost event at harvest shifted the microbial composition of cabbage and carrot ferments, with more cold-adapted taxa such as Leuconostoc, an increase in genes for menaquinone (K2) and cobalamin biosynthesis, and higher vitamin K1 in the cabbage ferments. That is a result about production parameters, not a promise about intake. It shows that raw material and harvest conditions matter, not that sauerkraut is a vitamin K source comparable to fresh cabbage.

On probiotics, the strongest human data remains the 17-week randomised trial published in Cell in 2021 by the Stanford group, which compared a high-fibre diet with a high-fermented-food diet in healthy adults, 18 people per arm. The fermented-food arm showed a steady increase in microbiota diversity and a decrease in inflammatory markers. That is an encouraging result, and it applies to an entire category of fermented foods eaten at several servings a day, across 18 participants, rather than to sauerkraut on its own. It does not license a promise of better immunity or digestion for anyone adding a spoonful to their plate.

Two practical consequences follow. Live bacteria do not survive cooking, so if that is what you are after, add the kraut at the end or serve it raw. And commercial sauerkraut in cans or pasteurised jars has been heat treated, which strips the live bacteria while leaving the fibre, the acidity and the sodium intact.

Biogenic amines and nitrite: the two rarely mentioned points

Spontaneous ferments produce biogenic amines, formed when bacteria decarboxylate amino acids. A review published in 2026 in Critical Reviews in Food Science and Nutrition notes that their presence in fermented foods is often unavoidable, which makes process control essential, and that spontaneous fermentation, the norm for vegetables, is more exposed to uncontrolled accumulation.

The measurements exist. A study published in 2025 in Environmental Microbiology Reports analysed commercial sauerkraut and fermented cucumbers by liquid chromatography coupled with mass spectrometry: putrescine dominated, followed by cadaverine, and the calculated biogenic amine index exceeded the estimated upper toxicity limit in four sauerkraut samples and one cucumber sample, ranging from 392 to 541. The 2026 survey of 75 fermented products reaches a comparable conclusion and flags high biogenic amine levels as a risk associated with spontaneous vegetable fermentation.

For most people this changes nothing: these compounds are metabolised by intestinal diamine oxidase and the amounts eaten stay modest. For people with histamine intolerance, or on a monoamine oxidase inhibitor, long-fermented foods are exactly the category to watch, and that is a conversation with a doctor rather than with a recipe.

What reduces amines in practice is whatever speeds up acidification: a correct salt ratio, a temperature in the right range, fresh cabbage, and no ferment left sitting at room temperature for months.

On nitrite, the order of magnitude is reassuring. A study published in Foods in 2026 on Chinese sauerkraut measured 1.86 mg/kg of nitrite in spontaneous fermentation, against 0.72 mg/kg with a Levilactobacillus brevis starter, and 0.44 to 0.70 mg/kg at pilot scale. The nitrite peak, a known feature of leafy vegetable ferments, occurs in the first days and then resolves. One more reason not to eat a three-day ferment.

Variations, spices and buying in Switzerland

Adding other vegetables does not change the principle, but it does change the arithmetic: the 2 per cent applies to the total weight of the prepared vegetables, not to the cabbage alone. For 900 g of cabbage and 200 g of grated carrot, that is 1,100 g times 0.02, so 22 g of salt. Carrots, beetroot and black radish bring extra sugar, which tends to speed the fermentation along; beetroot colours the whole jar.

With aromatics, restraint is not caution but a measurable effect. Juniper berries and caraway are the classic partners and barely touch the fermentation. Work published in Foods in 2026, however, tested essential oils of thyme, dill, wild thyme, laurel and basil in cabbage fermentation and concludes that adding them before fermentation can partly inhibit or slow the growth of the bacteria driving the process, while improving the flavour profile. Whole spices in small amounts are fine; concentrated oils have no place in a fermentation jar. The NCHFP table also lists mouldy spices as a fault cause in its own right, which rules out whatever has been sitting at the back of the cupboard.

On buying, white cabbage is a Swiss seasonal crop from September into deep winter, home grown and cheap in that window; a 1 to 1.5 kg head fills a two-litre jar. Stored winter cabbage works too, but generally yields less juice, having lost water in storage. For salt, ordinary iodised table salt from any supermarket does the job; the only things to avoid are potassium chloride based low-sodium salts and salts whose additive list you do not know. Standard rubber-gasket jars are convenient here, since the seal vents excess pressure on its own.

Five recurring mistakes

Salting by the handful. The gap between 1 and 3 per cent changes texture, speed and outcome. A ten-franc scale settles it permanently.

Counting the whole cabbage. The core and the outer leaves go in the bin. Weigh after shredding.

Stopping at seven days. The flavour is already pleasant, but the holding period that limits pathogen survival in the published challenge tests is at least fourteen days.

Sealing tight and forgetting. The CO₂ needs somewhere to go. A rubber-gasket jar releases pressure; a tightly screwed lid does not.

Treating sauerkraut as a green vegetable. At 661 mg of sodium per 100 g it belongs in the salt budget, alongside cheese or a salty sauce.

Adapting to different situations

High blood pressure or a low-sodium diet. Salt cannot be cut below 2 per cent without degrading safety and texture. The adjustable variable is portion size, not the recipe. Rinsing before serving removes part of the salt.

Vitamin K antagonist anticoagulants. The NHS states that foods high in vitamin K, such as broccoli, spinach and other green leafy vegetables, can affect how warfarin works, that you can still eat them, and that you should ask your anticoagulation clinic for advice. Sauerkraut is markedly lower in vitamin K than raw cabbage, but the principle remains consistency of intake rather than avoidance.

Histamine intolerance. Long ferments are the category most concerned by biogenic amines. Quick vinegar pickles, which are not fermented, offer a comparable sourness without the same profile.

Pregnancy. Fully fermented, properly acidic sauerkraut is not a particular risk food, but the general logic applies as it does to any raw unpasteurised product: a completed, clean ferment, kept cold and eaten within a reasonable time. Individual advice belongs with medical follow-up.

Children. Acidity and salt naturally cap the amount anyone eats. Swiss salt reference values fall with age, which makes sauerkraut a condiment rather than a main dish.

What to do with it once it is ready

Raw, it delivers the acidity that vegetarian cooking often chases with lemon or vinegar: in a bowl of grains and pulses, in a hummus sandwich, in a grated carrot salad. You can also explore other ways of preparing cabbage beyond fermentation.

Cooked, it loses its live bacteria but keeps its flavour value: braised with potatoes, juniper berries and vegetarian sausages, folded into a buckwheat pancake batter, added at the end to a root vegetable soup. In that case, cut the salt elsewhere in the dish.

The fermentation liquid, usually poured away, is an acidic brine that works in a dressing or as a starter for the next batch. It is also very salty, which calls for the same restraint as the rest.

If fermentation interests you beyond cabbage, the site covers homemade fermentations more broadly, the safety rules for lacto-fermentation, 24-hour quick pickles which are not fermentation in the strict sense, fermented drinks and lacto-fermented tomatoes. On the nutrition side, see vegan probiotics, iodine in a vegetarian diet and seasoning without salt, which is the logical counterweight to a food this salty.

The limits of this article

The composition values quoted are those of canned sauerkraut from the USDA database. Homemade unpasteurised kraut can differ, particularly on vitamin C and sodium, which depend on the cabbage, the salt ratio and any rinsing. No Swiss composition table publishes a specific value for raw homemade sauerkraut.

The biogenic amine data come from analyses of commercial products rather than domestic ferments, and there is no regulatory limit for biogenic amines in fermented vegetables against which a home batch could be placed.

The temperature recommendation comes from the USDA and has no published Swiss equivalent, since Swiss guidance does not address domestic cabbage fermentation.

Frequently asked questions

Can I use iodised salt? Yes. The 2018 Food Microbiology trial found no statistically significant effect of iodised salt on the microbial populations of the fermentation, and the Swiss food safety office recommends iodised salt to vegetarians.

Exactly how much salt? 20 g per kilogram of shredded cabbage, that is 2 per cent. The USDA recipe works out at that ratio.

Do I need to sterilise the jar? No. Careful washing in hot soapy water is enough in a spontaneous ferment, where the useful bacteria come from the cabbage itself.

How long before I can eat it? The flavour is acceptable after a week, but the challenge tests published in 2026 show that a holding period of at least fourteen days after acidification is what limits pathogen survival.

Is the white film dangerous? These are surface yeasts. The NCHFP recommends removing them as often as needed. Fuzzy coloured mould is a different case and justifies discarding the batch.

Why is my sauerkraut soft? The two most frequent causes in the NCHFP table are brine that is too weak and a fermentation temperature that is too high.

Is shop-bought as good as homemade? In cans or pasteurised jars it no longer contains live bacteria, though it keeps the fibre, acidity and sodium. Raw krauts from the chilled section do contain them, with considerable batch-to-batch variability.

Can I drop the salt to 1 per cent? Technically yes, but it is a poor idea: weak brine heads the list of causes of soft texture and it lengthens the phase in which unwanted organisms remain present.

Sources