1, purple kale is rich in water-soluble pigments anthocyanins, water discoloration is not necessarily added artificial coloring, is its original natural color.

2, and anthocyanins are usually stored in the plant cell vesicles, when the cell breakage will be dissolved into the water, you will see the phenomenon of the usual "color loss".

3, food coloring according to its solubility can be divided into water-soluble and fat-soluble.