If a recipe calls for “soybeans”, presume it means the “white” ones, which are actually more of a yellowy-beige colour. These are also called “yellow”, to distinguish them from black soybeans.
Soybeans have the longest cooking time of any beans. They need to be boiled for about 3 hours. Presoaking them will cut the cooking time down by half an hour. But refrigerate soybeans while you are presoaking, otherwise they may ferment (you won’t have this problem with other beans during normal soaking times.)
Soybeans never really cook entirely soft — the best you can hope for is “tender to the bite.” If you need to mash them, it’s very hard to do so with a fork or a potato-masher; you are better to pass them through a food mill.
Cook 1 cup (3 oz / 85g) of soybeans with 4 cups (32 oz / 1 litre) of water for 3 or more hours. However, if ever you are going to buy canned, already-cooked beans, this might be the time to do it.
Laurel Robertson, of Laurel’s Kitchen fame, recommends using handfuls of soybeans here and there in recipes, so that her family gets something with their superior nutrition in it, but something that they will still like to eat.
1 pound dry soybeans = 2 1/2 cups dry soybeans
1 cup dry soybeans = 2 cups cooked soybeans
1 cup cooked soybeans = 175g = 6 oz by weight
The Chinese have been growing soybeans for millennia. They were one of 5 “sacred” crops: millet, wheat, barley, rice and soybean.
Soy first reached Europe in the form of soy sauce. Benjamin Franklin sent soybean seed from London to a friend back in North America in 1770. By the early 1900s, our increased ability to analyse food revealed the high nutritional value of soybeans. Soybeans are now a very large crop in North America for animal feed and for oil.
Lyman, J.F & Bowers, W.G. The Digestibility of Soy Bean Meal by Man. In The Ohio Journal of Science. Vol 18 no 7, May 1918. pp 279-284.