Synthetic pigment is an edible dye extracted from petroleum or coal tar and synthesized by chemical methods. At present, there are about 60 kinds of synthetic pigments allowed to be used in the world, but according to toxicity tests, some synthetic pigments have obvious toxic or carcinogenic effects on human body. A small amount of human synthetic pigment will not cause immediate reaction, but it can be attached to the gastrointestinal wall, enriched in the body, and interfere with the functions of various active enzymes, thus affecting the metabolism of sugar, fat, protein, vitamins and hormone synthesis. And induce gastrointestinal diseases. Therefore, the production and use of synthetic pigments are strictly controlled, while others are prohibited. In order to protect people's health, only four synthetic pigments such as amaranth, carmine, lemon yellow and indigo are allowed to be used in China, and the dosage and scope of use are strictly stipulated. Synthetic pigments shall not be used in meat, fish, dairy products, baby food, preserved fruit, cakes, condiments and other foods, and synthetic pigments shall not be used in cold drinks and soft drinks with large consumption.
Many scholars advocate the use of natural pigments. Natural pigments come directly from animals and plants, most of which are safe, and some of them have certain nutritional value or pharmacological effects. China has a long history of using natural pigments to color food, such as chlorophyll, turmeric, Chili powder, carotene and purple mushrooms.