The skin of black beans is black, while the kernel of beans is white or yellow-white. If the color turns pale and the beans turn yellow, it may be fake black beans after dyeing.
True black beans, with black skin, natural color, smooth surface and no peculiar smell, do not fade after soaking, and the skin is hard and difficult to cook.
The fake black bean skin is sticky or thick and not smooth. Because it is dyed or soaked with industrial dyes and chemicals, it has an odor. Fading after washing or soaking, soft and perishable skin.