The soybean, Glycine max, is an annual plant belonging to the legume family, which also includes peas and beans. This seed is a globally significant crop, prized for its high protein and oil content, making it a foundation for both human food products and animal feed. Understanding the appearance of the soybean involves examining its journey from a leafy field crop to a small, dried seed. The visual characteristics change dramatically depending on the stage of maturity.
The Appearance of the Growing Plant
A soybean plant is an erect, branching annual that typically reaches a height between two and four feet. The structure of the leaves is a distinctive feature, as they are trifoliate, meaning each leaf is composed of three smaller leaflets. The entire plant, including the stems, leaves, and pods, is covered with fine, short hairs, giving it a slightly fuzzy texture.
During the reproductive phase, the plant produces small, inconspicuous flowers that are generally self-pollinating. These blossoms are either white or a shade of purple. Following successful fertilization, the flowers develop into the characteristic seed pods. As the season progresses, the leaves often begin to yellow and drop off before the seeds inside the pods are fully mature.
Visual Characteristics of the Pod and Mature Bean
The fruit of the soybean plant is a short, oblong pod that grows in clusters, often containing three to five pods together. These pods are densely covered in fine hairs and measure about one to three inches (three to eight centimeters) in length. Each pod typically contains two to four seeds, which swell and press against the pod wall as they develop.
As the plant reaches full maturity, the pods dry out, changing color from green to a brittle, hard texture that is usually brown, tan, or gray. The mature, dried soybean seed is small, generally pea-sized, and has an oval or nearly round shape. While the most commercially common color is yellow or tan, soybeans can naturally be black, brown, green, or even bicolored and speckled, depending on the variety. A small scar called the hilum, which can also vary in color (black, brown, or buff), is visible on the seed coat where it was attached to the pod.
Distinguishing Between Edamame and Dried Soybeans
The visual difference between edamame and dried soybeans is primarily a matter of harvest timing. Edamame are immature soybeans harvested when they are still soft, tender, and bright green. They are typically sold encased in their fibrous, green pods and must be steamed or boiled before consumption. The immature beans themselves are a vibrant, soft green color and are edible once shelled.
Dried soybeans, conversely, are the fully mature seeds left on the plant until the pods and seeds have completely dried and hardened. This maturation process causes the seeds to lose their bright green color, resulting in the hard, typically yellow or beige beans. These dried beans are most often used to make processed products like tofu, soy milk, and soy oil. The significantly lower moisture content gives the mature, dried seed its hard texture and extended shelf life, contrasting with the tender texture of the immature green edamame.