The captious vegetarian

Common Bean Myths

May 1, 2006 at 3:35 pm (Beans, Food Science)

There’s always controversy surrounding beans. Myths and superstition abound. In this post I discuss the pros and cons of soaking beans, when to add salt, and a few other controverisal issues.

Soaking Beans

The number one issue of debate when cooking beans is whether they have to be soaked first, and if so for how long. There are a number of issues that must be considered when deciding whether to soak your beans:

1. the effect on cooking time (and hence energy usage)
2. the effect on complex carbohydrates that cause flatulence
3. the effect on beneficial nutrients
4. the effect on palatability, including flavor, texture/consistency, and whether the beans hold their shape

Cooking time:  The consensus seems to be that soaking does reduce cooking time, but not by a huge amount.   If you’re in a rush to get your beans cooked, then it’s better to just start them cooking rather than leave them soaking.  But if you have the time, then a pre-soak will reduce energy usage slightly, possibly up to 25%.

How much does soaking beans actually reduce cooking time? There’s no one answer. The time saved depends on the size and age of the bean, on the cooking method, and on whether your soaking water is salted or not. Soaking saves more times with larger beans and older beans, since they take longer to hydrate. Soaking will save you more time if you’re using a slow-cooking method (like oven baking) rather than a fast-cooking method (like a pressure cooker). And soaking in a brine (i.e., heavily salted water) will reduce the cooking time more than soaking in plain water.

Epicurious tested with plain pinto beans and found that an overnight soak saves only 10 minutes of cooking time (on the stove). Russ Parsons in this 1994 article baked white beans with seasonings in the oven, and found that the pre-soaked beans were done 45 minutes sooner.

Harold McGee’s latest book (Keys to Good Cooking: a Guide to Making the Best of Foods and Recipes) apparently says that soaking beans reduces the cooking time by around 25%. This eGullet poster explains “This is primarily because the bean is already hydrated. Heat penetrates the bean much faster than water does, so when you cook unsoaked beans you are spending some of that time simply waiting for the beans to hydrate. This can create an effect whereby the outer part of the bean is overcooked and becomes fragile by the time the center is fully cooked, although this can be mitigated by cooking just below the simmer.  Anyway, a 25% reduction in cooking time is not all that much. So it’s unclear that presoaking is worth the trouble on a time basis. If unsoaked beans cook in an hour and a half, the same beans presoaked would still take around 67 minutes. A 23 minute difference is not such a huge amount of time saved that presoaking is worth the bother. ”

A cook at Saveur says:  “Here’s what we found out: soaking dried beans overnight is fine, and even good, in that it reduces the cooking time by at least a quarter, but if you have the time for a longer simmer, then soaking isn’t necessary. As for the quick-soaking method—i.e., bringing the beans to a boil and then letting them sit for an hour—we found that an hour in warm water made virtually no difference in the cooking time, so go for either the overnight soak or none at all. ”

Michael Ruhlman writes:  Certainly you don’t have to soak your beans overnight; if you want beans for dinner, put them in water and cook them till they’re tender or at least edible, no soaking, no blanching, just put them in a pot and cook them.

One thing that everyone seems to agree on is that if you are in a rush, don’t bother to do a quick-soak. Even a quick soak takes an hour, and clearly saves less than an hour of cooking time. So it’s a net loss. However, if you know in advance that you will have a limited window of time to cook your beans, then it is worth it to pre-soak your beans.

If you decide to pre-soak your beans, how long should you soak them for?

Many people simply soak beans overnight or put the beans on to soak before they leave for work—in both cases leaving the beans soaking for about 8 hours. But is 8 hours really necessary? Or optimal? According to McGee, soaking beans for more than four hours doesn’t gain you anything. (According to one blogger–need to look this up in his book. It’s unclear if this statistic assumes salted or unsalted soaking water.)

Also, here is another interesting comment from Rancho Gordo beans expert Steve Sando, who tends not to soak his beans.

Eric in Customer Service received a call recently about our Royal Corona beans not cooking. This confused us as we know exactly how old these are (we keep the lot numbers handy and we haven’t had this bean for long). The caller cooked the beans for hours and they weren’t softening. No salts, no acids, no reason! Then she said, “And I soaked them for 24 hours so they really should have cooked fast!” Bingo! There’s the culprit. Whenever we hear about cooking problems, they always seem to stem from over-soaking. It’s not intuitive but it seems to be the reality with our beans. If you want to soak, I would suggest from 4 to 6 hours.

So the science of this is not clear to me, but I think I have noticed this myself. Oversoaking beans (especially if they are fresh) can be a bad idea.

Other factors that affect cooking time

What most affects cooking times is how fresh your beans are. If the beans are really old then they might take many, many hours to cook, even if they were pre-soaked.

Another reason beans might take forever to soften up is if there are lots of minerals in your water (i.e., if you have hard water). Try using filtered water and see if it makes a difference.  Some people say you can soften your water by adding baking soda, but then I’ve heard that this destroys vitamins (B vitamins?). [I still need to find a reference for this claim. Anyone know of one?]

A third factor that affects cooking time is whether you leave the lid on or off. Leaving the lid on saves 15 minutes on the stovetop (according to Epicurious) and much longer in the oven (according to Parsons).

Recent testing by food science writer Harold S. McGee and the editors of Cook’s Illustrated has shown that brining the beans in salted water helps them cook more quickly than soaking in plain water. Cook’s Illustrated also says that brining helps soften the bean skins, which helps them cook more evenly and reduces the number of beans that rupture. Read more: How to Brine Beans | eHow.com. In September 2015, Cook’s Illustrated posted an update, in which they tried to reduce the amount of brine used. Their original formula recomended a gallon of water and 3 tablespoons of salt to soak 1 pound of beans. Their updated formula calls for just 2 quarts of water (and 1 1/2 tablespoons of salt) for a pound of beans. With the lower amount of brine, however, they recommend using a deep rather than shallow container (i.e., a relatively narrow bowl or pot rather than a wide Dutch oven) to ensure that the beans remain submerged as they hydrate and swell.

Flatulence: Beans are rich in fiber and complex sugars called alpha-galactosides which humans cannot digest.  Bacteria in the intestines digest these complex sugars, producing carbon dioxide.  The two primary alpha-galactosides in beans are raffinose and stachyose. Cook’s Illustrated analyzed how soaking affects stachyose. They found that a long soak led to a 28% reduction in stachyose, and a quick-soak (1 minute boil, 1 hour soak) removed 42.5% of stachyose. Thus, they argue that if you have intestinal discomfort issues from beans then soaking and tossing the soaking liquid will help. But they don’t actually cite any studies about how much a 28-43% reduction in stachyose actually reduces flatulence, if any.

Parsons claims that even if you do three quick soaks and discard the soaking liquid each time, you still only manage to reduce stachyose and other indigestible sugars by 90%. More importantly, people still get gas from these beans, due to their high fiber content. And the three quick soaks negatively affect flavor and texture.

Harold McGee recommends “soaking beans, then cooking them in the same water at a bare simmer for at least a couple of hours, even if they’re soft before then.”  That way you keep the nutrients in the soaking water, and the extended cooking breaks down the gassy carbohydrates. (Or so he says. I couldn’t find any other source claiming that cooking breaks down the indegestible sugars.)

Instead of trying to reduce gas by tweaking how you cook your beans, a better strategy seems to be to eat lots of beans and other high fiber foods on a regular basis.  Eventually the micro-flora in your gut adapt in some way so that less gas is produced.  (I don’t understand how though. Can anyone explain what chemical changes actually take place?)

None of these sources discusses a common scenario: you’re making a dish that doesn’t call for the bean broth (like a bean salad). In this case I would imagine that soaking is totally irrelevant to flatulence, since you’re going to toss the liquid in the end anyhow. I suppose it’s possible that the indigestible sugars get reabsorbed during the cooking process, in which case a quick soak and discard of the soaking liquid would result in higher reduction of the indigestible sugars.

Nutritional content: Cook’s Illustrated also studied how soaking affects beneficial nutrients. They say that during soaking many nutrients leach out of the beans, more so with a quick soak (presumably due to the brief heat) than with a long cold soak. Apparently heat breaks down cell membranes within the beans, and increases the solubility of water-soluble nutrients, such as calcium, magnesium, thiamine, riboflavin, and niacin. As a result, quick soaking tends to leach somewhat more of the nutrients out of the beans than do slow soaking methods. Again, however, if you either retain (and eat) the soaking liquid or discard the bean cooking broth it seems irrelevant which soaking method you choose. In the latter case, I would assume that the same quantity of water-soluble nutrients (if not more) would be leached out of the beans when you cook them. (I also assume, but do not know, that the nutrients don’t somehow get back into the beans during the cooking process.)  The only situation in which the soaking strategy would matter, it seems to me, is if you discard the soaking liquid, but use the bean cooking broth in your recipe. In that case, you should use a cold, slow soak to maximize nutritional content.

How does cooking affect the nutritional content of beans? A nutritionist interviewed by Cook’s Illustrated says: “More than 70 percent of bean nutrients are retained during cooking, including 86 percent of the protein, 83 percent of the iron, 96 percent of the zinc, 66 percent of the niacin, and 70 percent of the thiamine. About 53 percent of the calcium content, however, is lost. These numbers take into account that nutrient concentration diminishes during cooking because the beans take on moisture. For instance, one cup of dry kidney beans containing 44 grams of protein expands during soaking and cooking to two and one-half cups containing 38 grams of protein.”

There’s a huge camp of people who follow the paleo or Weston A. Price diet, who argue that beans are full of anti-nutrients like phytic acid, which substantially reduce nutrient availability.  They say that soaking beans can deactivate these anti-nutrients, and thus radically improve the amount of magnesium, zinc, and iron you actually absorb.  The best analysis I’ve found is on the rebuild-from-depression blog, which says that cooking doesn’t reduce phytic acid much.  The blog says that the best way to reduce phytic acid is to soak beans at 140º Fahrenheit for three hours, at room temperature for a very long time (around 18 hours), or in very warm water overnight. I think that after 18 hours at room temperature the beans would start to ferment.  Would keeping them in the fridge have the same effect?  One last note:  I vaguely remember reading that for neutralizing phytic acid the soaking water should be free of chlorine, so use filtered water or water that’s been sitting for long enough for the chlorine to evaporate.  (Need to find a citation.)

The folks who are very concerned about phytic acid generally recommend tossing the soaking water (I believe, need to find a reference).  But I thought that they argue that soaking actually neutralizes the anti-nutrients, not that they leach into the soaking water. If this is the case, then why the need to throw out the soaking water?  I don’t get it.

I was wondering if a slow cooker mimics the optimal temperature for phytic acid reduction described above.  Does cooking your beans in a crock pot keep them around 140 degrees?  My mom sent me this info:  “A typical slow cooker is designed to heat food to 77 °C  (170 °F) on low, to perhaps 88-93 °C  (190-200 °F) on high. Many recipes that include sauce or liquid will reach the boiling point around the edges, while food in the center remains gently cooked. This may be because slow cooker settings are based on wattage, not temperature.”  So it seems that a slow-cooker is too hot for optimal phytic-acid reduction.  But maybe it depends on how long it takes to get the beans up to temperature.  If you start the beans at room temperature, then how long are they in the 140º F range?  And as long as we are talking about crockpots, there are lots of warnings about cooking kidney beans in crockpots.  Apparently kidney beans contain relatively high amounts of some toxin that is only destroyed by boiling, and crockpots never get the beans hot enough.

Going back to phytic acid… The Weston A. Price people are rabidly anti phytic acid, but the vegan camp says that phytic acid is good, because it has some health-promoting effects.  They say that you shouldn’t try to reduce the phytic acid content but instead try to enhance nutrient absorption.  What you eat the beans with affects the bioavailability of trace nutrients.  It’s well known that eating beans with a food that contains vitamin C will substantially enhance absorption of non-heme iron.  That’s relatively well known among vegetarians. But something I hadn’t heard before: Dr. Greger claims one or two cloves of garlic or slices of onion can enhance nutrient absorption substantially.  I haven’t read the studies he’s citing yet, but the link to the articles on PubMed are underneath the video ([1] and [2]).

Flavor, texture, and whether the beans hold their shape:

Russ Parsons, author of “How to Read a French Fry”, says “Not soaking them [beans], really improves the flavor I’ve found.” But it’s unclear to me if he throws out the soaking water or not. Everyone seems to agree that tossing the soaking water reduces flavor. Cook’s Illustrated claims that quick-soaking beans has a negative effect on the texture. They also say that soaking beans for too long results in beans with tough skins, mealy interiors, and a lack of flavor. More specifically, they soaked black beans in the fridge overnight. They used one batch immediately, drained a second batch and left it in a ziplock bag for three days, and left a third batch soaking for three days. The first and second batches made excellent black beans soup. Both batches of beans were tender, moist, and creamy and had a rich, full-bodied broth. The third batch, resulted in a soup that was thin and bland, and the beans were too firm with tough skins. Now, presumably they threw out the soaking water. I wonder what would have happened if they retained the soaking water for the soup?

Epicurious is an outlier in that they actually recommend a quick-soak for optimal flavor. Their “winning method”:

For the Epi Kitchen, the results were clear. Quick-soaking the beans, salting them at the beginning of cooking, and cooking in a pot without a lid, resulted in beans with great texture and a flavorful broth. To cook: Place 1 lb. dried pinto beans in a large, heavy pot. Cover with water about 2” above top of beans. Cover pot, bring to a boil, then remove from heat. Let rest 1 hour. Stir in 1 1/2 tsp. kosher salt and bring to a boil over medium heat. Uncover, reduce heat, and simmer until beans are tender and creamy, checking after 1 hour and adding more water as necessary to keep beans submerged, 1–1 1/2 hours total.

Some people say soaking beans helps the beans hold their shape.  I think that probably the issue is that if you cook beans at too high a heat then they often break into pieces. Since soaking uses no heat, that can’t happen.  But if you cook your beans very, very slowly (like in a crockpot or in the oven, for example), they shouldn’t break up either.

Interesting note:  Apparently soaking beans is rare in Mexico—where beans are a staple of the daily diet.

One last comment about soaking beans. Whether or not it’s a good idea may actually depend on the type of beans. J. Kenji Lopez-Alt of Serious Eats strongly recommends against soaking “quick-cooking, thin-skinned” black beans, but states that “with firmer beans like cannellini or kidney, soaking can mean the difference between a pot full of blow-out bean fragments and a pot full of perfect smooth-skinned beauties.”

Adding Salt to Beans

Another controversial issue is whether adding salt or acids to beans slows down the cooking time, or toughens beans.  The acid claim seems to be true (depending on how much acid you add), but the salt claim is somewhat controversial.  A lot of chefs and cooking scientists discard this claim as an old wives tale, and argue that adding salt to beans at the start of cooking makes them taste better and have a better texture than adding beans after they’re cooked.  Others suggest salting the soaking water, but then not adding salt to the cooking water until close to the end of the cooking time.

Russ Parsons, author of “How to read a french fry” did some tests for an LA Times article that was published on 1/29/03. The article reports:  “Conventional wisdom dictates that dried beans should only be salted toward the end of cooking, because the salt draws moisture from the bean, producing an unpleasantly dry texture. But exhaustive tests done by Times columnist Russ Parsons showed that beans cooked with a teaspoon of salt per pound compared to beans cooked without salt cooked to exactly the same degree of softness in almost exactly the same time. Moreover, the beans salted during cooking required half as much salt.”   Parsons says “After doing my experiments, I started salting at the beginning rather than at the end and I think that makes a big difference in flavor as well (seasoned beans rather than salty broth).”

Cook’s Illustrated did a study with lentils and concluded that salt has no effect on cooking time or bean texture.  Furthermore, they suggest that for maximum flavor it’s actually essential to salt your beans at the beginning rather than the end of of cooking. Also, when soaking beans Cook’s Illustrated says that by using salt water the bean will cook up with softer and more pliable skins. Apparently the salt displaces some of the minerals like calcium and magnesium in the bean skins, which tends to make the skins tough. Since salt ions are weaker than mineral irons, they allow more water to penetrate into the skins, leading to a softer texture. Apparently during soaking the salt doesn’t make it all the way to the center of the beans, so the largest effect is on the outer skin. Cook’s Illustrated recommends 3 Tbs. of salt per gallon of soaking water.

Apparently Sara Moulton on Sara’s Secrets also dispelled the myth that salt makes beans tough, as did Shirley Corriher in this article from finecooking. Shirley actually says that salt aids softening: “A good soak in salted water can fix a hard-to-cook batch of beans.”  A cook at Saveuer says:  “And the salt? Adding it didn’t change the texture of the beans or alter the cooking time, so salt as freely as your taste dictates.”

J. Kenji Lopez-Alt of Serious Eats in his column on top cooking myths concurs: “A simple side-by-side test can prove to you conclusively that salting beans (both the water used to soak them in and the water used to cook them) actually tenderizes the skins. It’s got to do with magnesium and calcium, two ions found in the bean skins that help keep the structure of the beans’ skin intact. When you soak the beans in salt water, sodium ions end up replacing some of the magnesium and calcium, effectively softening the skins. Your beans come out creamier, better seasoned, and have a much smaller likelihood of exploding while cooking.”  He even has a nice picture to support his claims.

Harold McGee has a more nuanced take on the matter.  He writes in a New York Times Q&A on salt: “Salt does slow the softening of dried beans, but adding it early also gets salt into the bean interior, while adding late leaves most of the salt on or near the surface. If you’re thinking ahead early enough to presoak the beans, salt in the presoaking water actually speeds the cooking, in addition to salting the beans evenly.”  Another article summarizes’s McGee’s advice in his new book: “Go ahead and soak the beans in mildly salted water, but don’t add it to the cooking water until the end because it will take longer for the beans to cook.”  From an eGullet post:  “McGee says that using salted water has two interesting effects: It slows the rate at which the beans absorb water; but cooking beans which have been hydrated in salted water reduces cooking time significantly. When we cook no-soak beans, the hydration of the bean is already accelerated by higher temperatures. Then, when we use salted cooking liquid right from the start, we are hydrating the beans with salted water and this hastens the cooking time. The net effect is probably an overall shorter cooking time.” More from McGee: “the presence of salt [in the beans from the hydrating water] reduces the swelling and gelation of starch granules within the beans, which means that it favors a mealy internal texture over a creamy one.” The poster continues:  “Mealy” is exactly the kind of “al dente” effect I get when I cook beans using the no-soak method with salted water. On the other hand, sometimes what you want is a creamy texture. This is a case where I wouldn’t use the no-soak method and would hydrate in unsalted water.

One holdout is Steve Sando, owner of Rancho Gordo, who says that he salts roughly halfway to three-quarters of the way through cooking, once his beans start “smelling like beans”.  He says this gives him the same flavor result but fewer broken beans.”

How much salt should be added?  Somewhere I found this statistic:  Adding salt at concentration of 1%( 2 teaspoons/qt) will also speed up the cooking time by 25%.

Other Issues

Effect of acid, sugar, and calcium-containing foods:  Cook’s Illustrated says that acid does slow down the cooking process, but that the cooking liquid has to be pretty acidic to have a noticeable effect, so adding a few Tbs. of vinegar or tomato paste won’t interfere in any way, but cooking your beans in pure tomato sauce might be slightly detrimental.  However, if you want to cook your beans in a stew for a long time without them falling apart then adding some acid can actually be useful!  I found other posts saying that calcium and sugar also slow down the softening rate of beans, so blackstrap molasses should be added towards the end of cooking when making baked beans, but I haven’t confirmed this.  But a cook at Saveur says:  “A final revelation: for one version we tried, we removed the tomatoes and noticed that the beans cooked a lot faster. Acidic ingredients, it turns out, slow down the cooking process dramatically.”  The recipe they’re using only calls for one tomato in a pound of beans.  I wouldn’t think that would be enough to make a difference.

Amount of water:  Both Paula Wolfert and Harold McGee say that “less is more” when it comes to the amount of cooking water used to cook beans. McGee says the the beans will actually absorb more water when cooked in a smaller volume of water. Apparently, less cooking water means fewer carbohydrates are leached out, and these carbohydrates absorb a lot of water which then can’t be absorbed by the beans. It doesn’t quite make sense to me, but I think I have seen some evidence of this in my own bean cooking experiences.

Centralbean.com says to cover with 6 cups fresh water for each pound (2 cups) of beans, or to about one inch above the beans, but I think that’s for pre-soaked, rehydrated beans.  Non-soaked beans will take twice as much water??

Note that if you cook your beans without a lid then you will probably have to add water sometime during the cooking process.  If you leave your beans tightly covered then you shouldn’t have to add more water.

The U.S. dry beans council says “During cooking, the quantity of water should not exceed a third of the volume.”  They don’t say why.  I would think the percent would depend on whether your beans have been soaked or not.  I assume this statistic is regarding pre-soaked, hydrated beans.  Otherwise it seems way too low.

Shape of pot:  Harold McGee (in his new book, Keys to Good Cooking: a Guide to Making the Best of Foods and Recipes) recommends using a wide pot with a lot of surface area, for faster, more even cooking.

Foam:  What causes it?  How to reduce it (adding oil?)  Should it be removed? What happens if you don’t remove it?  If you don’t remove it will your beans be more likely to boil over?  It seems that if you cook the beans in the soaking water there is more foam.  Does that have anything to do with fermentation, or mineral content of the water?

Cooking/Soaking beans with kombu.  

Some sources claim that dried kombu (the kelp that is used to make dashi stock) neutralizes difficult-to-digest small carbohydrates in beans.  I haven’t seen this tested, but Cook’s Illustrated did test the effect of kombu on flavor and texture.  They say that cooking beans with a strip of kombu “not only boosts bean flavor but also improves texture: Pinto beans soaked and then cooked in water with a strip of kombu had soft skins and smooth interiors; soaked beans cooked in water alone were more grainy and tough.”  They say that the kombu is essentially achieving the same effect as overnight brining, “its sodium and potassium ions trading places with minerals in the beans to create a smoother, creamier consistency.”   However, “dried beans that went directly into the pot with the seaweed were nearly as tender as those that had been soaked in plain water or even brined. ”  In the end that say that if you have time for an overnight brine, then the kombu isn’t really needed, but if you don’t have time for an overnight soak, the kombu helps.  Their recipe:  “In 4 quarts of water, simmer 1 pound of beans, 1 tablespoon of salt (for seasoning), and one 3 by 5-inch strip of kombu until the beans are tender.”   I remember reading some warning somewhere about kombu having extremely high levels of iodine, so if you regularly cook beans with kombu this could be an issue.  I’ll try to find the exact source and write more.

Bean cooking chart

Here’s a table that lists cooking times and the amount of water to add for each type of bean.  A few caveats:  The cooking times also don’t match the table in Laurel’s Kitchen–I’m not sure why.  Also, it’s unclear to me why the amounts of water vary so much.  The table says to add 4 cups of water for 1 cup of black beans.  That sounds like too much to me.  So I’m doing an experiment:  4 cups of black beans (unsoaked, 1 lb 10 oz.), 10 cups of water (still seems like too much), put in a 5 quart pot, covered and brought to a boil, turned down to a low simmer (still covered) and cooked until tender.

From www.thekitchn.com:

How to cook dry beans in the oven:
Heat the oven to 325°. Put 1 pound of beans in a 3-quart (or larger) Dutch oven or pot with a tight-fitting lid. A clay pot is ideal. Add 2 teaspoons of salt. Add enough water to cover the beans by about 1 inch. Put on the lid and bake for 75 minutes. Check the beans and stir them. If they are tender, take them out of the oven. If they aren’t done, put them back in for 15 minute intervals until they are, adding a cup of hot water if they seem to be drying out. This will take at most 2 hours, but will probably take less than 90 minutes.

Fresh vs. canned equivalents:
• Canned vs. freshly-cooked beans: A 15-ounce can of beans will give you about 1 1/2 to 1 2/3 cups of beans, depending on the size of the beans.  For small beans like black beans I think it’s about 1.6 cups.  For larger beans like kidney or cannellini I think it’s close to 1.5 cups.
• Canned vs. freshly-cooked bean equivalents: 1 pound of beans will give you roughly the same amount as three 15-ounce cans of beans, or about 5 to 5.5? cups.

• This site says:  One cup of dried beans will expand to 2 – 3 cups cooked beans.  One pound of dried beans equals  5–6 cups cooked beans.  It says that for soaking you should cover with 3 cups of water per 1 cup of beans (or 10 cups water per 1 pound package dried beans).