How to cook dried legumes: all the tricks and secrets

Italy is bathed on three sides by the Mediterranean Sea, however the traditional Mediterranean diet has left for decades its place to a diet not very healthy or variegated, consisting mainly of foods of animal origin. This is demonstrated by the significant drop recorded in the consumption of legumes (the meat of the poor): from about 13 kg per capita per year in 1961, to less than 6 kg in 2011, more than halved (1).

Legumes are the cornerstones of the Mediterranean diet, as well as vegan, vegetarian, CHEtarian, flexitarian and, as noted in recent years, also of the diet for celiacs and people with gluten sensitivity.
Recently it seems that legumes are getting back on track again, going from those sad almost 6 kg per year, to 9 kg in 2020. This is not because they have been rediscovered as superfoods in their own right, or because they are rich in protein, fiber, phytonutrients, vitamin B and minerals such as calcium, iron, phosphorus, magnesium and potassium; simply because they now have a “very trendy look“!
Legumes are no longer to be found only in the proletarian section of canned goods and/or cereals and flours, but with a clever use of technology and industrial processes implemented to meet the new health trends, they occupy the least imaginable sections: snacks, sweets, plant-based patties, breads; even pasta is now made with legumes.

However while legume derivatives threaten the undisputed sovereignty of meat and wheat, according to data compiled by the group CBI of Netherlands Ministry of Foreign Affairs the consumption of the common beans in Europe, are perhaps at their lowest levels: annually it is around only 0.8 kg per capita. Even in the United States, this data could reach only 2.3 kg per capita in 2016.

So consumers like – again – legumes, but better if ready-made and packaged!

Instead, as I always stress, for CHEtarians health is important, but not in spite of sustainability; it should not be kept separate from that of the planet, so even if reducing meat consumption in favor of legumes is very important for the environment (read more here), at the same time we should not create other disequilibrium by preferring ultra-processed and packaged products, to those in the natural state.
And when it comes to natural legumes (not derivatives), very often we prefer to buy the ones ready to use: in glass jars or cans, etc… The excuse is always the same: lack of time, even if they cost much more.
Since I decided to found CHEFoodRevolution.com, I have always tried to identify myself with those who return home at 7:00 pm. (even though I work from home, I never stop working before that time). Consequently, I always repeat that in order to follow an economical, healthy and ethical diet, we need organization more than time.
And the preparation of dried legumes is an art of organization, starting with a prolonged soaking.
 

How to cook dried legumes: the steps

1) Visual check

It used to be a must, given the risk of damaging your teeth. If you buy legumes in supermarkets, they normally do not contain foreign objects such as stones, metals or other; but if you buy from the farmer, I always recommend a quick check.
 

2) Washing under running water

We have to cook the legumes before eating, but to remove a good part of the dirt and microbial load, they must be rinsed under running water (you can use the washing water to water the plants).
 

3) Soaking

The importance of soaking is very often ignored or snubbed: those few who still carry on this custom which is on the verge of extinction, do it just thinking about reducing cooking time. On the contrary, soaking allows to reduce time, energy consumption and, as a consequence, greenhouse gas emissions, but in particular by soaking we reduce the quantity of antinutrients naturally present in legumes.
Phytic acid and lectins are antinutrients that cause a significant obstacle to the absorption of essential minerals for the human body, such as calcium and iron (2,3,4); luckily, these antinutrients are water-soluble.
So, the soaking is more efficient if you change the water every 6-8 hours; the total phase must last at least 12 hours, normally 24 hours is better (in the winter months I leave them in water even for 36 hours).
Often on the packages of legumes such as lentils, we read the words ” no need to soak”; do as if it was not written: foresee a soaking of at least 1-2 hours.
 

4) Final Washing

It serves mainly to free the legumes from solubilized antinutrients. Do it without hesitation, under running water.
 

5) Cooking

Legumes are legumes, not pasta; therefore they should not remain “al dente” (undercooked). This is not a culinary preference, but a physiological need. Moreover, on the internet it is often said it is not necessary to throw away soaking water: always use fresh water (many ignore the issue of phytates). The concentration of phytates still present in legumes, is further reduced by cooking, thanks to the fact they are thermolabile (5); but without a prolonged soaking, cooking alone is not as efficient: the best results are reached with a combined action of these two processes (6).
Do you like perfection? I do, especially if it makes me save time and money without any side effects. As a true lover of pressure cookers, I am proud to inform you that according to scientific studies, in order to obtain the lowest concentration of lectins and phytates, (when it is not possible to use fermentation or sprouting, which remain the most effective methods), the only possible way is to cook at high temperature and high pressure (as only a pressure cooker can do) (7,8).

Another method to reduce phytates is sprouting, read more here

But please be aware: if you decide to use the pressure cooker, in order to avoid that the foam may create some risk, you should remove it; to do this I suggest you turn off the heat and open the pot as soon as the pressure inside let you, remove the foam using a special skimmer, then turn on the heat again and close the lid and continue cooking.

Insights for true food-science lovers

What is soaking and why is it recommended?

Through soaking we reduce the cooking time, because after a suitable time, the dried legume becomes saturated with water, returning (sometimes exceeding) to the original size of when it was fresh. To absorb water, the seed has only one site, the micropyle. This hole is not only important for cooking: it is from here that the plant is able to “irrigate” the embryo during germination; but since it is really “micro”, many hours are needed to hydrate the cell walls, and here is the need to keep legumes for long hours in soaking.

To reduce energy consumption and therefore your carbon footprint, try passive cooking legumes. Find out here how to do it without buying nothing specific
 

What happens during soaking?

In legumes proteins and starch are protected by very resistant cell walls, whereas cell walls are made of many types of indigestible polysaccharides, such as cellulose, pectin and hemicellulose. After some hours in soaking, the absorbed water starts to decompose pectin and with it also the cell walls. During these hours even substances defined as anti-nutrients such as lectins and phytates become soluble; to reduce their concentration, we should never skip this step.
 

Can we speed up the soaking process?

– Using lukewarm water can be useful to speed up this process.

– Moreover, by adopting the brine technique, we could increase the capacity of the micropyle to pass more water inside.
 

What does brine consist of and why to use it

It involves the addition of sodium chloride, the common table salt: the presence of salt is used to increase the osmotic pressure thus accelerating the hydration of the legume… but there is more. In fact in legumes, besides the nutrients already mentioned, are also present many minerals such as iron, calcium and so on. Pectin becomes stronger when there is more calcium in the environment: very good for the plant, less so for our “tummy“. If in the soaking medium there are more sodium salts than calcium, pectin loses its “solidity” and solubilizes, in other words it softens.

The magic formula would be, for half a kilo of legumes, 3 tablespoons of salt diluted in about 4 liters of water.

The technique of brine, as opposed to what one may think, does not cause an excessive sapidity to legumes; according to an analysis done by an independent laboratory, legumes soaked for 24 hours in a solution of water and salt, do not absorb a high quantity of salt: 85 grams of cooked black beans, contain just 52 mg of sodium (1 gram of salt contains 388 mg of sodium). But I don’t recommend relying on this method every time (only in case you have old legumes), because the presence of salt increases the ionic strength of the solution: which means that it solubilizes not only pectin but also proteins, causing them to denature in greater amounts during cooking.

To summarize, we can speed up the soaking in order to have an edible product in a short time, but this does not mean we have done a good job in preserving the nutrients useful to our body.
 

Tricks and myths

When we talk about how to cook dried legumes, it is impossible not to mention their age. As they get older, they are given a specific name: HTC (from hard-to-cook). In this group also belong legumes which are kept in bad conditions, such as high temperature and high relative humidity.

HTC legumes not only double the cooking time, but also change the taste and texture; they even alter the protein and vitamin content, because of too many hours of cooking. However if you happened to have a batch of legumes with this characteristic, do not throw them away causing more waste; use salt in the soaking water and bicarbonate of soda in the cooking water. Sodium salts are useful in alkalizing the environment, a condition that facilitates the hydration of legumes; and it is useful to prevent the cross-linking of new pectin chains, and therefore obtain a softer consistency in an acceptable time… thanks to an alkaline medium: this means we will not have to add “acids” before cooking (lemon juice, vinegar, tomato sauce etc.) in order not to harden pectin again.
 

Correct use of salt and bicarbonate

The perfect method(9) for hard-to-cook legumes, also tested by CHE Food Revolution, is to use sodium chloride (i.e. common table salt) for the soaking water; then rinse and cook them with drinking water (if the tap water is too calcareous*) with the addition of sodium bicarbonate (11). (1 teaspoon of baking soda per 1 liter can reduce the cooking time by 75%: I remind you that we are always talking about legumes defined as HTC, not young dried legumes).

Tip*

Cooking water, as well as soaking water, has its importance: the ionic composition of the water directly influences the speed of hydration and consequently the cooking time. Therefore if at home tap water is excessively rich in calcium(10), in this case I suggest you to use drinking water, if you cannot opt for demineralized water (or add 1 teaspoon of bicarbonate(11))

Baking soda has two advantages: like salt, it facilitates the weakening of existing pectin bonds, preventing new ones, and allowing higher sodium ions than calcium ions; moreover it generates an alkaline environment; this helps to decompose pectin molecules into smaller sizes, finally softening the legumes we are cooking: and this is the reason why, by adding bicarbonate during cooking, we will notice many husks (the decomposed pectin); a fact that alone discourages the use of the pressure cooker.

Another disadvantage is of organoleptic character: even a minimal dose such as 1 teaspoon of bicarbonate for the whole pot, can give a final bitter taste and viscous consistency!
 

How to digest legumes better

Learning how to cook dried legumes is not enough to improve their digestion!
Using baking soda or salt for this purpose, it seems, is not very helpful. The air or flatulence – let’s say it without shame – caused by beans, is due to the presence of some polysaccharides in substantial amounts (they are indigestible sugars, since we lack the right enzymes). These pass intact from the digestive system and “eaten” by bacteria, guests of our intestine: they are the ones who produce air or flatulence as metabolites of digestion!

In a study, dated but still relevant(12), it is shown that after examining various cooking/soaking options/use of baking soda and in various timings, there is not much difference in the reduction of polysaccharides responsible for our discomfort. The only option to get the least amount of the indigestible sugar-flatulence risk mix is to soak longer than 24 hours and use the autoclave (this is a pressure cooker that reaches higher temperature and operating pressure than the home type). Moreover the addition of bicarbonate, besides not being so much better than the other methods, seems to be detrimental for the content of proteins as well as B vitamins (13).
A really efficient tip instead is to add a piece of kombu seaweed to soaking or cooking water, or both of all. Kombu seaweed contains enzymes (alpha-galactosidase) that we do not have, which are necessary to break down these polysaccharides into smaller molecules, so that they can be passed into the soaking and/or cooking water and finally discarded with the water itself. Otherwise you can also use bay leaf, known for its carminative properties.

Another recommendation to reduce gas, is to increase your consumption of legumes gradually, in order to allow the bacteria of the intestinal microflora, to be more efficient in digesting “their food” slowly, thus creating less gas and discomfort.

After learning how to cook dried legumes, all you have to do is choose the recipe that suits you best: you have many options, from desserts to salads; from soups to patties or even excellent gnocchi.

Enjoy the revolution

You might also like:

• What is TAHINI: a super food that you can make at home
• Aquafaba: What is it and How to use the cooking water of chickpeas?

Bibliography
1) Dati Istat del 2013
2) Phillippy BQ. Transport of calcium across Caco-2 cells in the presence of inositol hexakisphosphate. Nutr Res. 2006;26:146–149. doi: 10.1016/j.nutres.2006.02.008. [CrossRef] [Google Scholar] [Ref list]
3) Phytic acid added to white-wheat bread inhibits fractional apparent magnesium absorption in humans. Bohn T, Davidsson L, Walczyk T, Hurrell RF Am J Clin Nutr. 2004 Mar; 79(3):418-23. [PubMed] [Ref list]
4) R.Y. Khattab,S.D. Arntfield. (2009). Nutritional quality of legume seeds as affected by some physical treatments LWT – Food Science and Technology ISSN: 0023-6438, Vol: 42, Issue: 6, Page: 1113-1118.
5) Vidal-Valverde C, Frias J, Estrella I, Gorospe MJ, Ruiz R, Bacon J. Effect of processing on some antinutritional factors of lentils. J Agric Food Chem. 1994;42:2291–2295. doi: 10.1021/jf00046a039. [CrossRef] [Google Scholar] [Ref list]
6) Vidal-Valverde C, Frias J, Estrella I, Gorospe MJ, Ruiz R, Bacon J. Effect of processing on some antinutritional factors of lentils. J Agric Food Chem. 1994;42:2291–2295. doi: 10.1021/jf00046a039. [CrossRef] [Google Scholar] [Ref list]
7) Deol JK, Bains K. Effect of household cooking methods on nutritional and anti nutritional factors in green cowpea (Vigna unguiculata) pods. J Food Sci Technol. 2010;47(5):579-581. doi:10.1007/s13197-010-0112-3
8) Kataria, A., Chauhan, B. M., & Punia, D. (1989). Antinutrients in amphidiploids (black gram× mung bean): Varietal differences and effect of domestic processing and cooking. Plant Foods for Human Nutrition, 39(3
9) Paredes-Lopez, O., L. Palma-Tirado and Reyes-Moreno, C. 1991. Influence of hardening procedure and soaking solution on cooking quality of common beans. Chemistry and Materials Science. Plant Food Hum Nutri, 41, 155-164.
10) Galiotou-Panayotou, M., Kyriakidis, N.B., and Margaris, I. 2007. Phytase–phytate–pectin hypothesis and quality of legumes cooked in calcium solutions. J Sci Food Agric, 88, 355–361
11) Onwuka, U. & Okala, O.. (2003). Effects of selected salts on the cooking time, protein content and sensory properties of African yam beans and cowpeas. Food Service Technology. 3. 3 – 7. 10.1046/j.1471-5740.2003.00060.x.
12) Effect of processing on flatus-producing factors in legumes Sudesh Jood, Usha Mehta, Randhir Singh, and Cheranjit M. Bhat Journal of Agricultural and Food Chemistry 1985 33 (2), 268-271 DOI: 10.1021/jf00062a028
13) KU, S., WEI, L.S., STEINBERG, M.P., NELSON, A.I. and HYMOWITZ, T. (1976), EXTRACTION OF OLIGOSACCHARIDES DURING COOKING OF WHOLE SOYBEANS. Journal of Food Science, 41: 361-364. https://doi.org/10.1111/j.1365-2621.1976.tb00619.x