Ingredient

Sauerkraut

Sauerkraut is cabbage that has been salted, packed under its own liquid and left alone until the bacteria already living on the leaf have turned its sugars into lactic acid. Nothing is added but salt. The sourness, the smell and the keeping quality are all made by the cabbage, which is why it is the simplest ferment there is and the one most worth understanding before any other.

What it actually is

Shredded cabbage, salt, and time. That is the entire ingredient list of real sauerkraut, and the shortness of it is the point.

Salt draws water out of the shredded leaf by osmosis. Within a few hours the cabbage has released enough liquid to sit under its own brine, and that brine is the whole trick: it keeps oxygen away from the leaf, which rules out the moulds and the aerobic bacteria that would otherwise rot it, while the salt-tolerant lactic acid bacteria already on the cabbage carry on working underneath.

Those bacteria eat the sugars in the cabbage and produce lactic acid. The liquid gets steadily more acidic, and as it does the food becomes hostile to almost everything else. A finished kraut preserves itself by being sour — not by being sterile.

What it tastes like

Sour first, and the sourness is soft and round rather than sharp. Lactic acid tastes quite different from the acetic acid in vinegar: less volatile, less nose-stinging, more like yoghurt than like a pickled onion.

Behind the acid there is cabbage — sweet, faintly sulphurous, more so the longer it goes — and a savoury depth that raw cabbage has none of. Good sauerkraut is also still crunchy. Limpness is the commonest fault and it is a texture failure, not a flavour one.

Shop-bought kraut splits into two kinds and they are not interchangeable. Unpasteurised kraut lives in the chilled cabinet, tastes brighter and more complex, and is still culturing slowly. Pasteurised kraut is shelf-stable in a jar or tin, tastes flatter and more one-dimensionally sour, and its cultures have been killed by heat. For cooking, the second is fine. For eating cold, the first is noticeably better.

How it is made

The mechanics, so that a recipe from a reliable source makes sense when you read it. FoodHQ does not publish salt percentages, pH figures or keeping times for home preserving. Those are safety numbers, they are set by a food safety authority rather than by a cookery writer, and the right ones depend on what you are fermenting and where you are. In the UK the Food Standards Agency is the authority — use a recipe from them or from another body with the same standing, and treat this page as the explanation of why that recipe is shaped the way it is.

1. Cabbage is shredded finely. Fineness matters: more cut surface means more juice released, faster, and a brine that forms before the leaf has a chance to dry out.
2. It is weighed, and salt is added as a proportion of that weight. Weighing rather than measuring by spoon is the single biggest difference between a recipe that works and one that does not, because a cabbage can vary in weight by half.
3. The salted cabbage is worked by hand or left to stand until it goes limp and wet. This is the osmosis doing its job — you are waiting for liquid, not for a texture.
4. It is packed hard into a jar or crock, pressing out air pockets, until the liquid rises over the top of the solids.
5. It is weighted down so nothing floats, and covered in a way that lets carbon dioxide escape without letting air back in.
6. It is left at room temperature. It bubbles, clouds, and smells increasingly sour over days to weeks — faster in a warm room, slower in a cold one — and is moved to the fridge when it tastes right, which effectively stops it where it is.

How to use it

Sauerkraut is not only a garnish for sausages, and treating it as one wastes it.

• Cold, straight from the jar, in a sandwich, on a hot dog, beside rich meat or cheese. This is where unpasteurised kraut earns its money, and heat is the one thing that undoes it.
• Squeezed and folded through a potato salad or a slaw, where its acid replaces some of the vinegar and adds savouriness vinegar cannot.
• Cooked slowly with pork, sausage, bacon or duck fat. Long cooking mellows the acid dramatically and turns it silky. This is what a choucroute garnie is, and it is a completely different food from cold kraut.
• In a fritter or a pancake batter, drained and chopped, where the acid keeps a heavy batter tasting light.
• Its brine is an ingredient in its own right. It is salty, sour and savoury — use it in a dressing, in place of some of the vinegar in a marinade, or drunk as a small sour shot, which is a traditional use across central and eastern Europe.
• Rinse it if it is too salty for the dish, and taste before you salt anything it goes into. Kraut brings its own seasoning.

Sauerkraut compared with the things it is confused with

Pickled red cabbage

Not a ferment. It is cabbage in spiced vinegar, sharp and acetic, sweet-sour rather than savoury-sour, and it keeps because vinegar was added rather than because acid was made. Very different flavour, very different use.

Kimchi

Also a lactic ferment, and the closest relative. Kimchi is seasoned before it ferments — chilli, garlic, ginger, fish sauce or an equivalent — so it is spicy, savoury and complex where kraut is clean and plain. Same mechanism, different result.

Coleslaw

Raw cabbage in a dressing. No fermentation at all, no acid made, no keeping quality.

Tinned or jarred shelf-stable kraut

Real sauerkraut that has been heated to make it stable. Still sauerkraut, still useful for cooking, no longer a live food.

Storing it, and what the signs mean

An opened jar lives in the fridge, under its liquid, with a clean utensil used to get it out. The two things that shorten its life are warmth and air, and the second is the one people cause themselves by leaving the solids poking above the brine.

Cloudy brine is normal and expected. Bubbling is normal. A strong sour smell is normal. A white film on the surface is usually kahm yeast, which is harmless, tastes unpleasant, and is skimmed off — see mould on a ferment for how to tell it apart from something you should not eat.

Fuzzy growth in any colour, a smell that is putrid rather than sour, or a slimy, ropy texture in the brine are not normal, and the answer to any of them is to throw the jar out. That judgement is worth making quickly and without sentiment: a batch of cabbage is cheap.

Making it yourself, in outline

Two ingredients, and the whole process visible through the side of the jar.

• Shred the cabbage finely. More cut surface means more juice released, faster, and a brine that forms before the leaf dries out.
• Weigh it. Salt goes in as a proportion of that weight, and a cabbage can vary by half — this is the difference between a recipe that works and one that does not.
• Work it until it goes limp and wet. You are waiting for liquid rather than for a texture.
• Pack it hard and weight it down so the brine rises above the solids. Anything above the liquid will mould.
• Cover so gas can escape but air cannot easily return, and leave it somewhere cool.
• Taste it from about a week and refrigerate when it tastes right to you. There is no fixed endpoint.

Common questions