Beans, dried

I admit to resorting to canned beans, unflavoured (they always come with salt and sugar though), as a starting point for most recipes that call for them. The need to soak the dried beans ‘overnight’ before cooking is the stumbling block for me.

But, it turns out that the soaking step can be separated from the cooking step by weeks to months – soak a large batch, rinse, drain, portion and freeze. The frozen beans can be cooked directly as required (no need to thaw). If you have a pressure cooker, then cooking the beans will usually take no more than 20m. Frozen, pre-soaked beans become a convenience food and can quickly produce a meal. Details at the end of the post.

The overnight soak is interesting. ‘Overnight’ is a term you regularly see in recipes. Soaking the beans in the morning and cooking them in the evening doesn’t appear to be an option. There may be something to it though – when soaking beans for a long time, it is best to soak them in the refrigerator to retard fermentation which can proceed at an alarming pace once it gets going. Overnight temperatures are cooler than daytime temperatures and may have served a similar purpose before modern refrigeration.

BeanThe main function of soaking is rehydration of the bean, and the main factor limiting this is that the outer skin of a bean is water-resistant. A little water can get in through the small area where the bean attached to the plant, otherwise it is well protected from moisture. Presumably, this is to ensure that the bean doesn’t begin to sprout until it is assured of plentiful water. One way to speed things up is to drop the beans into boiling water for 1-2 mins, then move them to tap water at room temperature. The initial boil will hydrate the skins and the subsequent soaking time can be reduced.

The reason dried beans are not cooked in a one-step process is that heat will penetrate the bean easily, however, water penetration is much slower and until water gets right into the bean the starch granules cannot swell and soften. While waiting for this to occur the outside of the beans overcook and become mushy. A secondary aim for soaking is to leech out some of the indigestible carbohydrates that pass on to gut bacteria that in turn produce gas as a byproduct and thereby give beans their reputation. It is a trade off though, we gain nutrients from the action of gut bacteria and the soaking will leech out other nutrients from the beans and be lost to us.

Beans are high in nutrients and contain unusually high levels of protein for plant matter. The proteins are not produced directly by the plant, they are the result of soil bacteria (Rhizobium) that invade the roots. These bacteria absorb nitrogen from the air and the plant converts this to amino acids and thereby proteins.

soybeanMost beans are mainly protein and carbohydrate. The exception is the soybean, which is not only high in protein (about twice that of other beans and with a good balance of amino acids), but also high in oil (~20%). Soybeans also come with anti-nutriants (as do most plants), and enzymes that break down the oil when activated. Harold McGee describes the resulting breakdown aroma as ‘reminiscent of grass, paint, cardboard and rancid fat’. Unsurprisingly, most soybeans grown in the West are fed to livestock or used to make oil. However, the Chinese (who were the first to cultivate the plant about 1,000 BCE) have been particularly inventive in transforming the bean into more palatable products – soy milk, bean curd, tofu, miso and soy sauce for examples – probably driven by the vegetarian requirements of a Buddhist diet.

Options for pre-soaking beans:

  • Soak ‘overnight’ or for 10-12h, refrigerated. Some recipes call for changing the water at half-time, which doesn’t make overnight that practical. Or:
  • Blanch in boiling water 1-2m, then move to room temperature water for 2-3h. No need to refrigerate. Or:
  • Pressure-cook 2m on high-pressure setting. Leave to cool without venting the pressure. I haven’t tested this approach – it may make a pre-soak/freeze step unnecessary, especially if it is followed up by pressure cooking the beans. But, there is something about the 2m that suggests there may be a lack of reproducibility, and it will take about 15m for the pressure to release, adding to overall time.

With each method, salt added to the soaking water will reduce subsequent cooking times (1tsp per litre of water)

Storage:

Rinse and drain the soaked beans. Portion into zip-lock bags, removing as much air as possible. Place flat in freezer until frozen. Store flat or vertical according to space.

Most recipes specify weight or volume of beans in their dried state. You could measure out 250g portions of dried beans and soak these separately, but that is inconvenient. Fortunately most bean recipes need not be exact and you could use the rule of thumb that dried beans swell to about twice their weight. So, portioning 500g soaked beans will be roughly equivalent to 250g dried beans. Or, weigh 1kg dried beans (for example), soak and divide into 4 equal quantities (each of which will be equivalent to 250g dried beans).

Cooking frozen pre-soaked beans:

Break the beans apart in the bag (rough clumps are OK). Proceed as indicated by your recipe. Thawing is not necessary – cooking times will be increased a few minutes, but it won’t be noticed.

PressureCookerThe pressure cooker is a good option. For boiling beans (to use in a salad for example), add the beans, an equivalent amount of water, herbs of choice (bay, thyme, sage), aromatics of choice (garlic, onion, carrot, celery) and some fat or oil (you don’t need much).

This last step is because most beans contain surfactants (emulsifiers)* and can cause the cooking liquid to foam up and possibly interfere with the pressure vent. The fat will retard foaming. Even so, don’t fill the pressure cooker more than a third, and never attempt to release the pressure manually after cooking – leave it to depressurise naturally. Cook on full pressure for 20m (for larger beans) and as little as 5-10m for smaller varieties. Drain the beans but reserve the liquid to use in place of stock – it is nutritious and flavourful.

* Soy beans are particularly high in surfactants. This is extracted and sold as a powder – soy lecithin. It was used to stabilise the light ‘airs’ in the citrus and salt air posts. It is so effective, it can create a stable foam out of only water. But, I digress, again.

Some things to keep in mind when cooking beans:

baked-beansThe following slow cooking and softening…

  • Hard water (e.g. water containing calcium or magnesium).
  • Acidic liquids (e.g. containing tomatoes).
  • Sugars.

The following speed cooking and softening…

  • Salt, by sodium displacing magnesium.
  • Alkaline liquids, e.g. by adding bicarbonate of soda, which is both alkaline and contains sodium.

So, for example, a baked bean recipe might call for cooking the beans with tomatoes and with some sugar/molasses/honey – a combination that will prolong cooking times and allow the flavours of other ingredients to develop before the beans overcook.


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Further reading:
Harold McGee, On Food and Cooking, Scribner, NY.
http://www.hippressurecooking.com – for details about pressure-cooking beans (and a heap of other stuff).