The purple-black color of black glutinous rice is due to the accumulation of anthocyanins in the seed coat, fruit coat and the paste powder layer, but also due to the influence of varieties and harvest seasons, resulting in differences in color. Since anthocyanin is a water-soluble pigment, it is normal that purple-black liquid will be dissolved when washing black glutinous rice. Black glutinous rice is a kind of brown rice because it has not been milled to remove the bran. When purchasing black glutinous rice, the first thing to do is to recognize that the black glutinous rice must have a remaining embryo (commonly known as the rice nose), and then use your fingernail to remove the pasty layer (colorful layer), and if it appears to be a pure milky white color, it will be the real black glutinous rice. If the pasty layer is removed and the milky white color infiltrates into the rice, then it may be the fake black glutinous rice. Black glutinous rice. It is normal for the two types of rice to be stained when cooked together! Cooked purple rice heart is also black but will not be very black, and white glutinous rice will be lavender black rice according to taste is mainly divided into three kinds: black glutinous rice, black indica rice, black japonica rice; black glutinous rice skin black, the core of the rice is white; black indica rice, black japonica rice skin black, the core of the rice is slightly transparent and a little purple. True black rice, there is a color difference between the grains of rice, some black deeper, some lighter; if it is dyed fake black rice, dyed color will penetrate into the rice core, so the core of the rice will also be black. Black rice soaked in water, the water black purple is normal, because the anthocyanins in black rice will dissolve in water, so do not over-wash black rice.