Legumes are all edible when young in the pod, although we only eat beans, peas and fava

beans at that stage of growth. We are more familiar with legumes after they fully mature and dry.

In fact, a major contributing factor to their historical popularity, besides their nutritional value, is

that they store so well in dried form—almost indefinitely without deteriorating. A third way we

eat legumes is freshly sprouted. Dry legumes, like most seeds, quickly sprout in moist, warm

conditions, providing flavorful and crisp sprouts, but only modest nutrition. It is in the dried form

that most legumes find their ways to our dining tables.

Once legumes reach their mature stage, the pods become dry and brittle, they crumble

and release the seeds. Before the farmers can be harvest legumes, the pods must dry thoroughly

on the vine. Though they originally contain a lot of water (about 80 percent), by the time they are

fully dried, their moisture content is less than 20 percent.

If we look at a seed under the microscope, we find three parts. The central mass of

substance is the main storage area for the new plant, called the cotyledon. Inside this mass is the

embryo of the new plant complete with two tiny leaves, roots and stems. A tube attaches this

embryo to the mass of cotyledon, and once the plant emerges, the embryo receives its food

supply through this tube, like human embryo through an umbilical cord. The third part is the seed

coat, which acts like our skin. It keeps the whole thing together and protects it from external

threats. To serve this purpose, it needs to be tough—a significant fact for cooks, because it is the

last thing to soften on cooking. If we cook legumes too long, the skin bursts, spilling out the soft,

mushy insides.

The seed coat is tough but it doesn't protect the seed from hungry insects and animals

with sharp teeth and strong jaws. The bean needs other defenses to combat them. Its first defense

is two proteins (protease inhibitor and lectin) that interfere with digestion of an animal that is

foolish enough to eat the seeds raw. Scientists have shown in experiments that animals fed only

raw soybeans actually lose weight because it takes more energy to digest them than they provide.

Rather than learn how to cook them, as we did, animals learned to avoid the raw legumes—those

that didn’t died of starvation. One of these two proteins (lectin) provides another protective

mechanism—agglutination. It actually causes cells in the eater's body to clump together. When

scientists feed rats only raw beans, they die within a few days because of this.

There’s still another line of defense, this is more straightforward. Many legumes contain

the toxin cyanide, that kills any hungry creature that attempts a meal from them. Don't worry

much about this one, though. Only lima beans contain enough to cause a problem in the human

body. Older varieties of lima beans had to be cooked thoroughly to eliminate cyanide. Newer

varieties people grow in most parts of the world have had most of the cyanide bred out of them.

However, even if it contains cyanide, properly cooked lima beans is not poisonous. Cooked in an

uncovered pot the cyanide evaporates. A covered pot traps it, and it falls back into whatever is

cooking in the pot. While heat can deactivate the cyanogenic compound in lima beans, cooking

old varieties in a covered pot could deactivate you.

Don't take beans out of your diet because of what you've just read. Heat gets rid of the

two proteins that interfere with digestion and the cyanide as well.

TASTINGS The killer lima bean

During World War I, when lima beans were imported to Europe from Java, Puerto

Rico and Burma, serious poisoning incidents occurred resulting from their high

cyanide content. People even died. In the new hybrids of lima beans there is no

harmful amount of its cyanide toxin left. But in some parts of Asia, illness and

Serious Kitchen Play