Black beans, also known as black soybeans or black adzuki beans, are the black seeds of the soybean plant. They are a versatile ingredient used in both medicine and food. According to traditional Chinese medicine, black beans are considered a tonic for the kidneys. They have a neutral nature, a sweet taste, and enter the spleen and kidney meridians. "Compendium of Materia Medica" states that black beans "treat kidney disease, promote diuresis, relieve various types of fever and heat, and invigorate blood. Boiling the beans can neutralize the toxicity of arsenic, croton seeds, aconite, musk, croton, blister beetles, and other poisonous substances. They can also treat diarrhea and navel pain, and can be used in combination with alcohol to treat convulsions, wind spasms, and abdominal pain caused by Yin toxin." It is important to be aware that in the market, there are black adzuki beans or soybeans dyed black, which are falsely sold as black beans, so it is important to be able to identify them.
Genuine Black Beans
The beans are spherical or oval-shaped, slightly flattened, and vary in size. They are 6-12 millimeters long and 5-9 millimeters in diameter. The surface is black or dark gray, sometimes with a reddish tint. The surface is smooth or wrinkled, shiny, and on one side, there is a pale yellow-white oval-shaped hilum, commonly known as the "little white spot." The beans are hard in texture. When the outer skin is peeled off, there are two thick cotyledons inside, which are yellow-green, known as "male black beans." They have a faint aroma and a mild taste. When chewed, they have a distinct bean-like flavor. If black beans are placed in a container and mixed with white vinegar, the anthocyanins in the bean skin will undergo a chemical reaction, turning the white vinegar red.
Fake Black Beans
Black adzuki beans: These beans are flattened oval-shaped, smaller than genuine black beans, and the skin is black and shiny. When the skin is peeled off, the kernel is white. When soaked in water, the water turns dark black. When added to white vinegar, there is little to no change in color, and no reaction occurs.
Dyed black beans: These beans have the same shape as black beans and are relatively uniform in size. The surface color is mostly jet black. When soaked in water, the color will fade because the bean skin is thin and the dye will penetrate the inner layer. The soaked beans will have traces of dye, and the hilum (little white spot) will also be dyed black. There is a distinct smell of chemical dye.
Modern pharmacological research has shown that black beans have estrogen-like effects, with greater potency than soy isoflavones. They can inhibit the absorption of endogenous and exogenous steroids, have antioxidant properties, increase the excretion of cholesterol, and lower blood lipid levels. They also have antispasmodic effects and promote detoxification in the intestines. Black beans have been used to treat constipation and aid in weight loss. Fake black beans do not possess these medicinal properties, so they cannot be substituted for genuine black beans.
