Artificial pigment has good stability, but it is not easy to fade. Common natural pigments include tetrapyrrole pigments (heme and chlorophyll), carotenoids (such as carotene and lycopene), polyphenol pigments (such as anthocyanins), beet pigments and so on. According to their solubility, they can be divided into two categories: water solubility and fat solubility. Polyphenol pigment and beet pigment are both water-soluble pigments. When they are dissolved in water, they will appear "fading" phenomenon. For example, anthocyanins contained in mulberries, strawberries, blueberries, cherries, bayberry, purple cabbage, purple potato and other foods will cause cell damage if washed with water.
It is normal for anthocyanins to dissolve and fade. The red color of red beet, red amaranth and red pitaya is lycopene. When they are washed or boiled with water, pigments will also dissolve in water. Although some foods contain anthocyanins, the cell structure is relatively dense, so the color will not fade after a short period of washing. But after soaking for a long time, the outer cells gradually absorb water, and purple or blue-purple anthocyanins will slowly dissolve out, such as black rice, purple rice, black peanuts, black corn, black soybeans and other foods. The density of extracellular cells in different varieties affects the degree of their decline.
Many natural foods will change color, because the chemical properties of natural pigments are often unstable, and they will change when exposed to acid, alkali, heat, oxidant and oxidase. When developing and screening artificial pigments, the screening criteria are strong coloring power and good stability.
Compared with natural pigments, artificial pigments are not easy to fade. The artificial pigment added in strict accordance with the national food safety standards is safe and controllable.