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Every recipe says I should soak beans in water overnight before cooking. Why?

I did some experiments. I have tried soaked and unsoaked beans from the same batch. There was no difference in cooking time, taste, structure or color. Even farts were the same!

Also, one time I read an interview with a cook that makes famous bean soup and he confirmed my findings. He said that he also experimented and he doesn't find a difference.

So what is the reason for soaking beans before cooking? What does it change?

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I agree I rarely soak my beans ahead of time. Usually, I just rinse them and pop them in the slow cooker in the morning and they're ready when I get home from work. I also usually add bay leaves or kombu which allegedly increases "digestibility." –  Kiesa Jul 10 '10 at 13:47
Relevant: cooking.stackexchange.com/questions/9891/… –  Orbling Jan 9 '11 at 15:07
how is soaking different from cooking –  rebekah Jan 9 '11 at 23:02
Soaking means pouring cold water over beans and let then in it (without cooking) overnight. Only then, when beans are soaked (they absorb some water), you cook them. –  Fczbkk Jan 9 '11 at 23:02
Please provide some details of your experiment, most importantly what type of bean and the cooking method. Garbanzo "beans" will be very different than black beans, for example. Slow cooker v. stock pot v. pressure cooker probably matters, too. –  derobert Jul 29 '11 at 17:17

12 Answers 12

I grew up on pinto beans, a staple in my life. My mother NEVER soaked the beans before cooking. Now a grandma myself I still cook beans bi-weekly. Then I read somewhere that beans MUST always be soaked first. So, I did a few times and I found that the deep bold bean flavor and color of the beans, was gone. Surely, some of the nutrients had also decreased. I was greatly disappointed! I then asked my Mexican cousin how she cooked beans. When I told her that I had heard that they must be soaked, she thought that was real silly. She definitely did not soak them. I went back to my way. I have also heard that eating beans on a regular basis will make your body used to them and there won't be a problem with gas. I also think everyone's body is different, so what works for one person may not for another. I love beans, I never get tired of them and for growing up in a poor family, they were instrumental in having good health!

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It may be the case that soaking beans without salt has negligible effect. However, Cook's Illustrated has found that soaking the beans in a brine solution has a significant benefit to the beans, and all of their recent recipes using dried beans call for this step.

Here's what they have to say:

Brining isn't just for meat. When you soak dried beans in salted water, they cook up with softer skins.

Brining isn’t just for meat. When you soak dried beans in salted water, they cook up with softer skins. Why? It has to do with how the sodium ions in salt interact with the cells of the bean skins. As the beans soak, the sodium ions replace some of the calcium and magnesium ions in the skins. Because sodium ions are more weakly charged than calcium and magnesium ions, they allow more water to penetrate into the skins, leading to a softer texture. During soaking, the sodium ions will only filter partway into the beans, so their greatest effect is on the cells in the outermost part of the beans.

Brining Formula: For 1 pound of dried beans, dissolve 3 tablespoons of table salt in 4 quarts of cold water. Soak the beans at room temperature for 8 to 24 hours. Drain and rinse them well before using.

They add some further explanation in their blog post on the subject:

After cooking batch after batch in the test kitchen, we now know what works and what doesn't.

Brine Your Beans, Not Just Simply Soak, for Tender Skins

Recipes often recommend soaking beans in water overnight before cooking. A quick-soak alternative is to bring the beans and water to a boil and let them stand for an hour or so before cooking. Both of these classic methods produce beans that are more evenly cooked than starting with unsoaked beans -- and in far less time, too (in our experience, soaking can shave 45 minutes off the cooking time).

Soaking makes for tender, creamy bean interiors, but intractable bean skins often remain noticeably tough, regardless of the soaking time. We discovered that soaking the beans in salt water -- in essence, brining the beans, as we often do with meat and poultry -- tenderizes the skins.

This works because as the beans soak in salt water, some of the sodium ions in the water replace some of the calcium and magnesium ions in the bean skins. The sodium ions are weaker than the ions that they replace, so they permit water to enter into the skins, which leads to softer texture. During soaking, the sodium ions enter only into the skins, so the bean interiors are not affected.

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I haven't soaked beans for five years with great results. I have eliminated the gas. I've been sticking a pinhole in each bean prior to cooking. Works well, I don't notice any fragrance.

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You poke a hole in every single one?? –  Jefromi Nov 24 '13 at 6:10

Soaking beans for at least 12 hrs is essential in order to remove the anti-nutrients such as phytic acid and to make them more digestible. You must discard the soaking water, it is dirty and contains all the anti-nutrients. Cover the beans with filtered water and add 2 tablespoons of raw apple cider vinegar such as Bragg's. Soak for at least 12 to 24 hrs.

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As others have said, soaking mostly decreases cooking time. That's the main reason to do it. With some beans, the difference in time is minimal, but with tougher beans that take longer to cook (e.g., black beans), soaking can reduce cooking time significantly, particularly if the beans are a little older and more dried out.

The reason is because the first period of time in water is spent hydrating the seed coat. Once the seed coat is completely hydrated, water can flow through the surface and begin to cook the interior of the bean. The hydration of the seed coat can happen in cold water as well as hot water, so soaking beans will allow that process to begin before cooking. With most beans, the difference in cooking time might be 15-30 minutes (perhaps not enough to be significant for a dish that's cooking for a couple of hours anyway), but with some it might be as much as an hour.

Some say that soaking helps to maintain shape or keep beans intact, but I've found that really depends on the type of bean, how old they are, and how they are cooked. In many cases, the best-looking beans I've made have come from batches that were never soaked but cooked slowly (start in cold water and slowly bring up to a simmer).

The other main reason often cited is to prevent flatulence. However, if you throw out the soaking water, you also throw out lots of nutrients. Recent research suggests that long slow cooking is a better solution and probably gets rid of more of the flatulence-causing components than a soak followed by a quick cook. And you get to retain more nutrients. To quote Harold McGee from On Food and Cooking:

One kind of troublesome carbohydrate is the oligosaccharides [which are water soluble].... But the latest research suggests that the oligosaccharides are not the primary source of gas. The cell-wall cements generate just as much carbon dioxide and hydrogen as the oligosaccharides--and beans generally contain about twice as much of these carbohydrates as they do oligosaccharides.

Based on this research, McGee suggests:

[Soaking] does leach out most of the water-soluble oligosaccharides--but it also leaches out significant quantities of water-soluble vitamins, minerals, simple sugars, and seed-coat pigments: that is, nutrients, flavor, color, and antioxidants. That's a high price to pay. An alternative is simple prolonged cooking, which helps by eventually breaking down much of the oligosaccharides and cell-wall cements into digestible simple sugars.

In short, soaking might decrease your cooking time slightly. Otherwise, there's no good reason to do it. However, with no soaking, do be sure to rinse the beans thoroughly before cooking. I generally rinse 3-4 times with fresh water to get rid of as much dirt as possible.

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Either way is fine as long as the beans are washed throughly....It's just a matter of how long you want to spend cooking them...I wash/soak my black beans and then cook with a pressure cooker and the whole thing is done in an hour....and sooooo good too!!!!

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I came across this site while googling the very same question. No one has addressed a thought I had: beans (which are seeds after all) soak up moisture prior to sprouting, which changes their nutritional value. I once read somewhere that bean sprouts are veritable little nutrition bombs with a high concentration of all the good things a human needs to stay (or become) healthy.

So: perhaps soaking INcreases their nutritional value, rather than DEcrease it as someone here suggested. (I also like the idea of undigestible sugars being removed that way, and getting rid of phytic acid)

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Hi Betty, I'm not sure I follow your reasoning... Do you have any sources for your suggestion? If not, this may belong more as a comment, rather than an actual answer. Welcome to the site! –  talon8 Aug 22 '12 at 14:16
Referring to Betty's answer, this link may be helpful; drybean.unl.edu/PROCESSING/Removal%20of%20Anti-nutrients.html –  MissesBrown Aug 23 '12 at 10:15

Mark Bittman distinguishes three techniques:

Quick-Soak (boil, turn off heat, let soak 2 hrs, return to heat, simmer til done), No-Soak (boil then simmer, til done), and Long-Soak (soak in cold water for 6-12 hrs, drain, simmer til done). (taken from here)

The cooking time of beans varies from bean to bean. Bittman prefers the "quick soak" variant, and it is easy to see why: For most beans, it significantly reduces the cooking time (and thus the time you need to watch the pot and presumably the energy), and it doesn't require you think of soaking beans the night before. If you are happy and get good results without soaking, I don't think there's a compelling reason to switch.

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The reasons for soaking beans have been debunked by a number of chefs/cooks, including:

I've been making no-soak beans for years now and found no difference in gassiness, texture, or flavour. The only difference seems to be cooking time and convenience.

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Reading through the transcript on the Good Eats episode he seems to be a supporter of soaking. –  talon8 Jul 29 '11 at 14:59
He was in early seasons, then re-considered in latter seasons (with use of a pressure cooker). His conclusion was that soaking is a tradeoff of time: either more cooking time, or more prep time. Other reasons were discounted (like reducing gas, better texture). I sometimes soak, and sometimes not - difference is 30-45 minutes of cooking time without the assistance of a pressure cooker. –  Bruce Alderson Oct 27 '11 at 19:15

Soak (and rinse) beans to remove the phytic acid in their skins which block mineral absorption in the human body.

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First they will absorb water so the cooking will be different, if only for a reduced time.

Then, depending on the recipy you'll have more ingredients to cook with the beans which may have different cooking times (potatos for example) which can either end up raw or too cooked if the beans are in a different state.

Finally, depending on the bean the skin might end up softer or harder, giving away a different texture...

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One reason is to remove some of the indigestible complex sugars that cause gas.

Another reason is that beans are dirty, so you're just cleaning them with the soaking. If the recipe wants the beans to be cooked in the water used for soaking, the washing needs to be done before the soaking.

On top of that the soaking can reduce cooking time considerably, which might be the biggest advantage.

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I'd just add that because soaked beans take a lot less time to cook, they tend to hold their shape better. As an aside, soaking does have some disadvantages. Dark skinned beans and mottled beans will loose colour. Soaking also removes some nutrients. –  Pulse Jul 10 '10 at 9:48
This is strange. I didn't notice any difference in cooking time between soaked and unsoaked beans. Also, I think you should wash beans even before you soak them. Most of the recipes ask you to cook beans in the soaking water. Without washing them first, that would mean cooking them in dirty water. –  Fczbkk Jul 10 '10 at 10:17
Of course, if the recipe wants you to cook the beans in the water they've been soaking in, you need to wash them first. I'll add it :-) –  jmoeller Jul 10 '10 at 11:20
Yes, soaking will reduce cooking time. –  Himadri Jul 10 '10 at 12:02
@Pulse As you said 'Soaking also removes some nutrients.'. That can be a disadvantage when you don't use the soaked water for gravy. The soaked water contains the taste of the beans so throwing that up won't be too helpful. –  TheIndependentAquarius Jul 8 '11 at 7:29

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