These seeded pods of various legumes are among the oldest foods known to humanity, dating back at least 4,000 years. They come in two broad categories — fresh and dried. Some beans, such as black-eyed peas, lima beans and cranberry beans, can be found in both fresh and dried forms. Fresh beans are those that are commercially available in their fresh form and are generally sold in their pods. The three most commonly available fresh-bean varieties are green beans (eaten with their shell or pod) and lima beans and fava (or broad) beans, which are eaten shelled. Store fresh beans in a tightly covered container in the refrigerator up to 5 days; after that, both color and flavor begin to diminish. If cooked properly, fresh beans contain a fair amount of vitamins A and C; lima beans are also a good source of protein. Dried beans are available prepackaged or in bulk. Some of the more popular dried beans are black beans, chickpeas, kidney beans, pink beans and pinto beans. Dried beans must usually be soaked in water for several hours or overnight to rehydrate them before cooking. Beans labeled "quick-cooking" have been presoaked and redried before packaging; they require no presoaking and take considerably less time to prepare. The texture of these "quick" beans, however, is not as firm to the bite as regular dried beans. Store dried beans in an airtight container for up to a year. The flatulence caused by dried beans is created by oligosaccharides, complex sugars that — because they're indigestible by normal stomach enzymes — proceed into the lower intestine where they're eaten (and fermented) by friendly bacteria, the result of which is gas (see digestive enzymes). Dried beans are rich in protein, calcium, phosphorus and iron. Their high protein content, along with the fact that they're easily grown and stored, make them a staple throughout many parts of the world where animal protein is scarce or expensive. See also adzuki; cannellini; fermented black beans; french bean; great northern; marrow beans; mung; navy; pea bean; pigeon pea; red beans; runner; soybean; sprouts; white bean; winged; yard-long.