Soaking: Beans, Rice, and Everything Dried

Soaking is not cooking; it is adding water

The outside and inside of a dried ingredient hold very different amounts of water. Boil it straight away and the outside overcooks while the centre stays dry. Soaking removes that gradient in advance, so its purpose is not to shorten cooking but to make it even.

Skip it and you usually get a blown-out exterior around a hard core.

The rule about salt is wrong

It is widely repeated that you must not salt the soaking water for beans. In fact the opposite is true: beans soaked in salted water (1 tsp per litre) soften better.

The reason is pectin in the skins. Pectin binds calcium and magnesium and stiffens; sodium displaces them, and the skin softens. For the same reason, beans cook poorly in hard water.

What genuinely must stay out is acid. Vinegar, tomato and lemon set pectin firm. So in bean dishes the tomato goes in after the beans are tender — which is exactly the order chana masala, dal, Red Red, Pasta e Fagioli and Cassoulet use.

In some dishes the same property is the point rather than an obstruction. The sauerkraut in Bigos survives three hours of stewing because the lactic acid it made itself has already stiffened the pectin in its own cell walls. One reaction: an obstacle in beans, structure in cabbage.

Beans that never soften

Sometimes they stay hard no matter how long you boil. Usually the beans are old: in storage the pectin in the skins cross-links permanently, and nothing reverses it. A date left on the bag is no guarantee.

A pinch of bicarbonate of soda (1/4 tsp per litre) breaks pectin down with alkalinity and does soften them. But it dulls the colour, destroys vitamins and can taste soapy, so treat it as an emergency measure.

One dish makes that emergency measure its method, and puts the pectin somewhere else. Mushy peas stirs 1 tsp per litre — four times the dose above — into an overnight soak, every time. The three costs are managed rather than accepted: the soaking water is thrown out and the peas rinsed two or three times before they ever reach the pan. It also narrows what the alkali dissolves. The paragraph above puts the pectin in the skins, which is where it matters for a bean that has to stay whole; a marrowfat pea keeps its coat and collapses anyway, because the pectin that goes is the middle lamella holding the cells inside the pea together. One reaction, a different part of the same plant.

When to discard the soaking water, and when to use it

This is the part that needs judgement.

Discard:

• Beans and pulses — the indigestible oligosaccharides leach into it.
• Dried chillies, where bitterness and grit come out of the seeds and pith. Grinding the vindaloo paste in vinegar alone is partly about not using that water.
• Anything gritty: wood ear or seaweed gets a final rinse.

Use:

• Dried shiitake. That water is a large share of the savouriness; throwing it out throws out half the aroma (building umami).
• Dried shrimp and shellfish, for the same reason.
• Sun-dried tomatoes, kombu.

With mushroom water, let the grit settle and pour off the top.

On neither list: dried fruit — and the same ingredient goes both ways depending on the dish. Bara Brith steeps its fruit in tea overnight and uses that tea as the batter's liquid, not for aroma the way mushroom water is kept, but because it is the water the batter needs. Put dry fruit into a batter instead and it pulls water out of the crumb. Apfelstrudel soaks its raisins for thirty minutes and then drains them, because there the filling must not be wet.

So the test is not the ingredient. It is what that liquid becomes in the dish.

Soaking to take something out

Everything above is about putting water into an ingredient. The other direction exists, and one rule changes when it does.

The salt cod in Bacalhau à Brás sits in water for 24 to 48 hours, and the point is to get the salt out. Diffusion runs both ways and stops when the concentrations meet. Water going into a bean never runs out, so one bowlful is enough — but water taking salt out saturates. Left in the same water, 48 hours is no different from six.

So the recipe here is not a length of time but how many times you changed the water, and the test is tasting a flake, not the clock.

A grain that was cooked once before it was sold

Everything above assumes the dried thing is raw, and that the soak is preparation for the cooking that follows. Some ingredients were already cooked once before they were sold, and for those the soak is the whole of the cooking — which first cooking it was decides how they come back.

• Boiled, dried and cracked. The fine bulgur in kısır is wheat that has already been boiled, so twenty minutes under boiling water is not a head start on the cooking, it is the cooking. Simmer it like rice and it goes to porridge. The ratio is also fixed at 1:1 rather than a generous bowlful, because that grain takes up a set amount and any excess occupies the space the pepper paste has to fill. Everywhere else in this guide too much soaking water is merely waste; here it is a fault in the finished dish.
• Roasted, then milled. Kama is roasted whole grain, so it needs no hot water at all and disperses straight into cold kefir. The same class of ingredient, handled the opposite way.

Rice depends on what it is for

• For steaming: 30 minutes evens out the moisture so the grains cook uniformly (cooking rice).
• For grinding: batters like dosa need 5-6 hours, since the grain has to be soft enough to grind.
• For fried rice the problem is the opposite — that is a question of cold cooked rice, not soaking.
• For crushing: Jeonbok-juk soaks neither for evenness nor for grinding but so the grain can be broken in half. Dry rice skitters and powders under a pestle; rice soaked thirty minutes splits cleanly.

Rough times

• Split lentils: 30 minutes, or none
• Chickpeas, soybeans: 8 hours or overnight
• Black beans, adzuki: 6-8 hours
• Dried shiitake: 30 minutes in warm water, 2 hours in cold
• Dried chillies: 15-20 minutes in hot water
• Rice for steaming: 30 minutes
• Rice for grinding: 5-6 hours
• Dried wood ear: 20 minutes

Hot water shortens the time but costs flavour. Use it only when rushed. Anything over 8 hours at summer room temperature starts to ferment, so long soaks are safer in the fridge.

Those are floors, and some soaks carry a ceiling as well

Every number above answers one question: how long until the thing has taken the water up. A soak doing some other job carries a second number this table has no column for — how long before it has taken out of the ingredient the thing you wanted to keep in it. The line directly above is one form of that cost, filed under temperature: hot water is faster and costs flavour. The cost is not confined to hot water.

Kinpira gobo sets the whole axis out on one page, because it soaks exactly as the potato dishes it names do and for a different reason. Gamja jeon and gamja jorim put cut potato in water to rinse the starch off; burdock goes in to keep oxygen away from it, because its cut surface browns within seconds at room temperature. Its own wording: "Same action, different purpose — which is why potato can soak as long as you like while burdock past five minutes starts losing its aroma into the water." Where the job is to take something out, longer is simply more of what you were after; where the job is to keep something out, the clock is a cost from the first second.

• Or catch what leaves instead of watching the clock. Hwangtae-guk gives its freeze-dried pollock "five minutes of soaking, no more. Longer and the savour leaves for the water" — and then keeps that water, for the same reason dried shiitake and dried shrimp are on the "use it" side of the list above. Two parts of this guide meet there: a ceiling on the soak and a use for the liquid are two answers to one loss.
• The ceiling this guide already states is on the water, not on the food. Past eight hours at summer room temperature the soaking water ferments, and the fridge buys that time back without touching what is leaving the ingredient. Burdock's five minutes cannot be bought back that way.

Blanching caps its ice bath at about thirty seconds for a related reason, but what competes with the leaching there is arresting a vegetable that has already been cooked. Here nothing has been cooked yet, and whether there is a ceiling at all is settled by what the soak is for.