Fermenting is the preservation method that needs nothing. No fuel, no jars to process, no pressure canner, no electricity, no sugar, no vinegar. Salt, vegetables, water, a container and time.
It also makes food more nutritious rather than less, which is unique among preservation methods, and it is the one you can start this afternoon with what is already in the kitchen.
If a household could learn only one preservation technique for a long emergency, this is the one.
Why this is the best preservation method in an emergency
- Zero fuel. Canning costs a great deal of heat, drying costs some, freezing costs continuous power. This costs none.
- No specialist equipment. A jar, a bowl, a bucket. Traditionally a wooden barrel or a stoneware crock.
- It is safe by chemistry, not by process control. The lactic acid the bacteria produce drops the pH below 4.0, and at that acidity the dangerous organisms cannot grow. The ferment defends itself, and it does so continuously rather than at one processing moment.
- It increases nutritional value. Fermentation produces B vitamins and makes minerals more available. Vitamin C survives, which is why sauerkraut kept sailors and northern European households from scurvy through winter.
- It is self-indicating. A ferment that has gone wrong usually tells you loudly, unlike a jar of botulism.
- It handles a glut. A large crop of cabbage, beans, carrots or cucumbers becomes food that keeps for months, in a day's work.
The salt calculation
Use a kitchen scale. This is one place where "a good handful" genuinely is not adequate: too little salt and spoilage organisms out-compete the lactobacillus, and too much stalls the ferment entirely.
Salt type matters. Use pure salt with nothing added: sea salt, pickling salt, kosher salt, or plain rock salt. Avoid table salt containing anti-caking agents, which make the brine cloudy and can inhibit fermentation, and avoid iodised salt, which suppresses the bacteria you are trying to encourage.
The two methods
Dry salting, for vegetables that release their own liquid. Cabbage above all.
Shred, weigh, add the salt, and work it hard with your hands for five or ten minutes. The salt draws water out of the cells and you end up with enough of the vegetable's own brine to cover it. This is how sauerkraut is made and it needs no added water at all.
Brining, for vegetables that will not release enough liquid. Carrots, beans, whole cucumbers, cauliflower, turnips.
Pack them into the jar, then make up a separate brine at 2 to 3% and pour it over until covered.
Doing it
- Prepare the vegetables. Wash, but do not scrub obsessively: the wild lactobacillus lives on the skins and is what starts the ferment. Do not use anything sterilised or chlorinated.
- Weigh everything and calculate the salt.
- Dry salt and massage, or pack and brine, as above.
- Pack tightly into the vessel, pressing down to drive air out.
- Get everything under the brine and keep it there. This is the whole game. Use a weight: a smaller jar full of water, a scalded stone, a folded cabbage leaf tucked over the top, a proper glass fermentation weight.
- Leave headspace, at least 5 cm. A vigorous ferment can overflow.
- Cover, but let gas escape. Fermentation produces carbon dioxide and a sealed jar can build genuine pressure. An airlock lid, or a lid rested on loosely, or a cloth and a rubber band, or a screw lid "burped" daily.
- Keep it out of direct sun, somewhere cool, below 21°C.
- Watch for bubbles within one to three days. That is fermentation starting.
- Taste from about day 5. Use a clean utensil, never fingers. When it tastes right to you, it is ready.
- Move it somewhere cold to slow it right down: a cellar, a larder, a fridge. It will keep for months.
Kahm yeast or mould
The commonest question, and the answer decides whether you eat it or bin it.
Kahm yeast is a collection of wild yeasts, mainly Pichia, Debaryomyces and Candida species. It is not pathogenic and produces no harmful toxins. It is unsightly, it can give an off flavour if left, and it is very common. Skim it off, make sure everything is back under the brine, and carry on.
Mould is different and the batch goes. Do not scoop the mould off and eat what is underneath: mould sends structures down through the food that you cannot see, and some moulds produce toxins that diffuse well beyond the visible patch. A fuzzy raised patch of any colour means discard.
The single best prevention for both is the same: keep everything under the brine, keep the salt at 2% or above, keep it cool, and minimise the air above the surface. Both kahm yeast and mould need oxygen; lactobacillus does not. That is the whole reason for the weight.
Reading a ferment
| What you observe | Meaning |
|---|---|
| Bubbles, fizzing, brine rising | Working correctly |
| Brine turns cloudy | Normal and expected |
| Sour smell, like pickles or yoghurt | Correct |
| Vegetables lose colour, go duller | Normal |
| White sediment at the bottom | Spent lactobacillus. Normal |
| Flat white film on top | Kahm yeast. Skim, carry on |
| Fuzzy raised patches | Mould. Discard |
| Slimy, ropy, stringy brine | Wrong bacteria took hold, usually too little salt or too warm. Discard |
| Smells putrid, rotten, of drains | Discard |
| Soft and mushy | Too warm, too little salt, or over-fermented. Safe if it smells right, unpleasant to eat |
| Nothing happening after 4 days | Too cold, too much salt, or chlorinated water. Move somewhere warmer |
What to ferment
Excellent, and reliable:
- Cabbage, as sauerkraut. The classic. Dry salt method, 2%, three to six weeks.
- Cabbage with carrot, garlic, ginger, chilli, as kimchi.
- Cucumbers, whole, in brine. Add a grape, oak, blackcurrant or horseradish leaf: the tannins keep them crisp.
- Carrots, in sticks. Fast and sweet.
- Green beans, whole.
- Beetroot, sliced. Slow, earthy, excellent.
- Turnip and swede.
- Cauliflower.
- Garlic, whole cloves. Turns blue sometimes, which is harmless.
- Radish, kohlrabi, celeriac.
Difficult or poor:
- Anything soft: courgette, tomato, aubergine go to mush.
- Potatoes, which ferment badly.
- Very starchy vegetables generally.
- Onions, which can go slimy, though they are fine as part of a mixed ferment.
In a British garden year, the glut months are the case for this: a summer of cucumbers and beans, then autumn cabbage, carrot, beetroot and turnip. That is most of a winter's vegetables preserved with nothing but salt, and it is exactly what British and northern European households did before either canning or refrigeration existed.