The Chinese long bean is also called the yardlong bean, asparagus bean, Chinese noodle bean, or snake bean, and can be almost 1 yard (about 1 m) long. The best Chinese long beans are young and slender, with a crisp, chewy texture. These beans can be red or green, but should be bright and evenly-colored, with slightly wrinkly skin. When cooking Chinese long beans, use only dry heat, as boiling or stewing can produce poor quality.
Chinese long beans are related to cowpeas and are named after their pods, which can be as much as 14 to 30 inches (35 to 75 cm) in length. These beans grow quickly and are most commonly farmed in warm parts of southern China, as well as other areas of southeast Asia. Long beans can be eaten raw or cooked, but are usually stir-fried. The Chinese long bean also works well in salads.
To choose the best Chinese long beans, look for young pods about the same diameter as a pencil, since older beans can be tough and unpleasant to eat. Very old long beans can be shelled, the pods discarded, and the seeds boiled and eaten like pinto or navy beans. Long beans look a lot like conventional green beans, but stay chewier and crunchier after cooking. They should break with a crisp snap when fresh, be flexible without limpness, and will have either bright green or bright reddish-purple skins.
Look for specimens with a slightly wrinkled surface, but a firm texture. Avoid older beans, which become soft and wrinkly over time. Don't select any Chinese long bean with dark or soft spots, fuzzy white mold, or pits and holes along its length. While you can still eat these beans once the bad spots have been removed, they are much lower in quality. Store long beans in the refrigerator for up to a week, but use them before they become limp.
The method of preparing Chinese long beans that you choose can also affect their quality. While conventional green beans are often stewed or boiled, any cooking in water can render the Chinese long bean mushy and unpalatable. Prepare these beans by breaking or chopping them into small pieces and cooking them over dry heat in a very hot pan or wok, using just a little oil. The skins should shrivel and pucker, turning brown in some areas. You can then top them with a savory sauce and eat them with rice or noodles.