How do you keep green beans green? Granted, it may not be the most pressing question of our time, but it is one that cooks everywhere scramble to find an answer to every summer. Although the method is surprisingly simple, it turns out that sometimes green beans shouldn’t be all that green anyway.
Every green vegetable goes through essentially three stages of green. When it is raw, the vegetable is a deep but dull green. During the early stages of cooking, the color turns bright and vibrant. This change occurs as the cell walls soften and the tiny amounts of oxygen and other gases they contain, which cloud the pure color of the chlorophyll, are driven off. Finally, the green turns olive drab. This happens because of a chemical change in the chlorophyll, which is partly due to an enzymatic action, but mostly due to acids that either are introduced during cooking (adding vinegar or tomatoes, for example) or come from the vegetable itself and are released during cooking.
Since vibrant color is so important, cooks have devised different strategies for getting around this chemical change. Old French chefs added a bit of baking soda to the water. This helps preserve the green, but it also speeds the breakdown of the plant’s cellulose, making the texture slimy. Some modern chefs insist that cooking in very heavily salted water will help. There doesn’t seem to be any scientific basis for this claim, although it probably does no harm and will certainly help the seasoning of the vegetables. The best way to avoid olive drab vegetables is to cook them in plenty of water (to dilute the acids that are released); to make sure the water returns to the boil as quickly as possible (this will finish the cooking more quickly); and to cook them briefly—then, if possible, plunge them into ice water as soon as they are done (this stops the cooking process immediately).
Although a vibrant green color is usually desirable, there are times when it can be forgone in favor of flavor. In the case of green beans, for example, the importance of preserving the color depends largely on what kind of bean you’re cooking.
The green bean is a legume that is harvested when immature. If green beans are left to grow to maturity, the seeds inside will swell to nugget size, and the tender pods will toughen and become coarse (as any gardener who has ever gone on summer vacation will readily attest).
Green beans can be roughly divided into two groups: the round and the flat. The round types, most famously Blue Lake and the French haricots verts, tend to be more delicate in texture and brighter in flavor than the flat types. These should almost always be cooked briefly to preserve their color. Flat beans, such as the Italian Romano, are meatier and more assertive. You can cook them longer than round beans—long enough even that the color will fade to olive drab. In fact, because of their thick, meaty texture, their flavor actually seems to improve with long cooking.
“Green” beans also come in different colors. There are chlorophyll-free yellow beans and several varieties that are purple. And there are beans that are purple and yellow, such as the dragon tongue bean. Yellow beans keep their color during cooking, but purple and patterned beans fade to green—a dull green at that. The Asian yard-long bean, which looks like a stretched-out green bean (it comes in purple as well), is actually more closely related to the black-eyed pea. Its flavor reflects that lineage, but its colors are bound by the same scientific laws as regular green beans.
Green beans are sometimes called “string beans,” although that is a misnomer—or at least an antique usage. A tough filament runs up the seam of old green bean varieties and needs to be removed before cooking (just as with edible pod peas). The string was bred out of most popular varieties around the turn of the century, but you can occasionally find heirlooms that still have it. The old name “snap bean” is much more to the point and still valid, as green beans wilt quickly and should be crisp enough when you buy them that they’ll snap cleanly in half.
Some legumes are left to grow to full maturity, whereupon they are shelled and dried for use through the winter. Dried beans come in sizes ranging from a grain of rice to as big as your thumbnail; in a wide assortment of jewel-like colors—reds, pinks, purples, maroons, even black; and in an almost countless array of patterns. (Unfortunately, for the most part these brilliant colors fade to various shades of tan and brown during cooking, although some of the patterns are distinct enough still to be visible.) Dried beans are picked fully mature, after most of the sugars have turned to starch. The drying after harvest removes all but the last traces of moisture, so they can be stored almost forever.
That also means that dried beans require extensive cooking in plenty of water to become edible, as those rock-hard starch granules need not only to soften but also to reabsorb the lost moisture. You can shorten the cooking time somewhat by soaking the beans beforehand (though, contrary to popular opinion, this does little to allay dried beans’ famous gastric side effects, and soaked beans never come close to the richness of beans that have been cooked without soaking). Depending on the size of the bean and how long it’s been stored, soaking can save as much as an hour of cooking. But soaking also means that you have to plan dinner the night before. You’re really just choosing between inconveniences.
Some beans are harvested at an intermediate stage. Shelly beans, which are between green and dried, offer some of the most sublime eating you can imagine, but they are difficult to find except in the South or at farmers’ markets. They are the same varieties that are normally dried but are sold at full moisture. They cook in 20 to 30 minutes without any special treatment and have a silkiness of texture and a sweetness and delicacy of flavor that are unmatched. Probably the stellar example of this is the lima bean. Scorned by many who know it only in its dried, canned or frozen form, the lima at the shelly stage is nothing short of spectacular, with a complexity of flavor that puts even favas to shame.
WHERE THEY’RE GROWN: Only about a quarter of the green beans grown in the United States are eaten fresh, and almost half of those come from Florida. Georgia and California trail far behind. Imports represent about 10 percent of the beans sold, but that percentage is increasing, particularly during the winter months. Mexico supplies more than 90 percent of the imported fresh beans.
HOW TO CHOOSE: Green beans are surprisingly delicate and begin to lose moisture as soon as they are picked. The pods should have no sign of wilting or mold. The name “snap bean” is a great clue: bean pods should be so crisp that they snap when bent.
HOW TO STORE: Green beans are somewhat hardier than peas and fava beans, but they still need to be cooked soon after you buy them. Store them tightly wrapped in the crisper drawer of the refrigerator.
HOW TO PREPARE: Most green beans no longer have strings, but they do have stems and tough stem ends, which must be removed. The trailing point at the other tip of the bean can be either cut off or left on.
ONE SIMPLE DISH: There is no easier or more delicious accompaniment to any grilled or roasted meat than a bowl of green beans. The best way to prepare them is to blanch them in a big pot of rapidly boiling salted water for about 7 minutes. They should be bright green and al dente—well cooked, but with a slight crispness. When you pick a bean out of the water, it should droop but not sag. Stop the cooking in ice water and pat the beans dry. Dress them with a mixture of olive oil, lemon juice and just a bit of garlic right before serving. (If you dress them too early, the lemon juice will change the color.)