Legumes are a truly ancient food. It’s thought that lentils were cultivated as far back as 7000 B.C. The legume family includes beans, peas, peanuts, and lentils. Its members are excellent sources of protein, fiber, and minerals; combined with grains, legumes are a staple food for many cultures. Legumes are packed with nutrients. Per serving, they have twice as much protein as cereals (legume and cereal combinations, like beans and rice, complement one another to provide many essential amino acids). With the exception of soybeans and peanuts, most legumes are very low in fat. Their high fiber and soluble fiber content can help reduce cholesterol levels and help stabilize blood sugar levels, making you feel “full” longer. In addition, legumes are high in vitamins B and E, calcium, potassium, and iron.
While many legumes contain small amounts of toxins—lima beans contain cyanide, for example, and dried beans contain lectins—cooking destroys these compounds, making the beans harmless. Cooking also gets rid of enzymes known as protease inhibitors, which would otherwise prevent us from digesting proteins.
Legumes present cooks with a few pressing questions: must we soak them? why do they sometimes never seem to get tender? and how can we eliminate, or at least reduce, their less flattering side effects?
Soaking helps softens them up
Though they vary considerably in size and shape, all legumes have essentially the same structure. They are all seeds, which consist of two halves, called cotyledons, that are the starch storage centers for the young seedling. When they’re immature, legumes are tender enough to be eaten with minimal cooking. But once they’ve been preserved by drying, legumes benefit from some sort of preliminary soaking or rehydration to soften them before cooking.
The most common way to soften dried beans is by soaking them in room-temperature water for several hours or overnight. Water initially enters the bean through the hilum, or scar, where the bean was attached to the stem in the pod. Only after some water has been absorbed by the seed through this small opening will water start soaking through the seed coat. Legumes with thinner coatings, such as lentils or split peas, will soften faster than those with thicker membranes.
The warmer the water, the faster the bean absorbs it. This principle has led to the “quick-soak” method of softening. Rinse the beans several times and discard any “floaters.” Then, in a large pot, cover the beans with 4 cups of water for each cup of beans. Bring the water to a boil, reduce the heat and keep at a low simmer for 2 to 10 minutes. Turn off the heat, cover, and let stand for an hour. You could also heat the beans and water together in the microwave until the water is boiling and then let them soak for about 1 1/2 hours.
Some beans refuse to soften. You can soak them overnight and then simmer them all day long, and they’re still hard as pebbles. The main causes of this are age and improper storage. If beans have been stored at high temperatures (around 100°F) and high humidity (80%), chemical changes occur that make them almost impossible to soften. You can often avoid this situation by keeping dried beans in an airtight container and a cool place.
Salt can help counter the hard-to-cook phenomenon. You may have heard the myth that salt hampers beans’ ability to soften. I don’t know how this rumor started, but it isn’t true. The fact is that soaking beans in salted water before cooking can help rectify the hard-to-cook situation. The next time you have a recalcitrant batch of beans, try soaking them in salted water (1 tablespoon salt per gallon of water) for 2 hours.
Salting beans early is actually a good idea for other reasons. I add sea salt to beans at the beginning of cooking as a flavor enhancer, along with bay leaves, thyme, ham hocks, or salt pork. Salt and other seasonings can diminish the “beany” taste that some people object to.
How long to cook dried beans on the stovetop
In general, you should have 3 to 4 cups of water for each 1 cup of beans. Count on getting 2 to 2-1/2 cups of cooked beans for every cup of dried beans. Below are approximate times for conventional stovetop cooking.
|type of bean||condition||water||cooking time|
|adzuki||unsoaked||4 cups||90 minutes|
|adzuki||soaked||4 cups||60 minutes|
|black (turtle)||soaked||4 cups||90 minutes|
|black-eyed||soaked||3 cups||60 minutes|
|chickpeas||soaked||4 cups||2 to 3 hours|
|Great Northern||soaked||3 cups||90 minutes|
|kidneys||soaked||3 cups||60 minutes|
|lentils||unsoaked||3 cups||60 to 90 minutes|
|lentils||soaked||3 cups||45 minutes|
|lima||soaked||3 cups||60 minutes|
|navy||soaked||3 cups||60 minutes|
|pinto||soaked||3 cups||2 to 2-1/2 hours|
|soy||soaked||4 cups||3 to 4 hours|
|split peas||soaked||3 cups||45 minutes|
Calcium, sugar, and acidic ingredients inhibit softening
Though salt isn’t one of them, there are certain ingredients that can prevent beans from softening. Normally when fruits and vegetables are cooked, heat causes the insoluble pectic substances (the “glue” between the cells) to convert to water-soluble pectins, which dissolve. The cells then separate and the fruit or vegetable softens. Both calcium and sugar, however, hinder this conversion to pectin, so when beans are cooked with an ingredient containing these substances, such as molasses, the beans won’t get overly soft. That’s why Boston baked beans can be cooked for hours and still retain their shape. If you cooked the same beans without the molasses, you would have “refried” beans (bean mush). Cooking beans in “hard” water, which contains calcium, also prevents softening.
Acidic ingredients prevent softening, but in a different way. While calcium and sugar prevent cells from coming apart, the starch that’s inside the cells can still swell and soften, so the beans will be tender. But acids work differently, acting on starch within cells, preventing it from swelling. So don’t add acidic ingredients, such as tomato sauce, wine, lemon juice, or vinegar, until the beans are tender.
How to adjust the timing for other cooking methods
Pressure cooker (use about 2-1/2 cups of water per cup of beans)
soaked: 20 to 30 minutes
unsoaked: 40 to 50 minutes
unsoaked: 12 hours on low
soaked: 50 minutes
Minimizing the flatulence factor
Legumes get a bad rap for their tendency to cause flatulence. One of the causes of this sometimes embarrassing situation is the large sugars, called oligosaccharides. Our bodies can’t digest these sugars, so they pass untouched through our digestive system until bacteria in the lower intestine devour them, and in the process produce quantities of gas. The amount of gas produced varies greatly among individuals, depending on the bacteria in their intestines. And some varieties of beans seem to produce more gas than others, such as navy and Great Northern, even though they don’t have higher oligosaccharide contents. This suggests that other compounds in legumes contribute to gas, too. This is an area that’s still not thoroughly understood.
Rinsing beans will help. Luckily, oligosaccharides are water soluble, so rinsing the beans several times in fresh water is a help in reducing gas. The “quick-soak” method of softening mentioned earlier also helps. There are enzyme products intended to break down the oligosaccharides and reduce gas, although their effectiveness varies.