The food coloring is a kind of regulating the food color and food additives, color is an extremely important sensory indicators of food. Food coloring must first be dissolved and dispersed in the food, according to the different solubility properties of pigments can be divided into water-soluble pigments and fat-soluble pigment; can be divided into the difference of color, the green pigment (eg chlorophyll), orange-red pigment ( such as beta-carotene), red pigment (eg, lycopene); according to different sources, can be divided into natural food coloring and synthetic food coloring.

In modern society, the natural production of what are often enjoys a high reputation in the eyes of the people, and meet the peoples habits. Therefore, the natural food coloring more and more attention has been paid. For example, the the Roselle pigment extracted from the mature tropical cash crops Roselle calyx (sound è), its main ingredient is the the larkspur prime -3 - elderberry two glycosidic; a yellow pigment extracted from turmeric roots of plants. called curcumin, is a two-ketones; red pigment extracted from the cochineal, called carmine acid. Natural food coloring after long-term use, relatively safe and reliable.

Variety of synthetic food coloring, cheap and therefore widely used. For example, edible tar pigment is extracted from coal tar distillate, tar acid, have now discovered that it is carcinogenic to prohibit use. Is also used as synthetic beta-carotene is a yellow pigment used in making drinks, pastries, bread, ice cream. Synthetic food coloring should be progressively restrict the use has been recognized, but it is worth noting that, in our country there are still a few unscrupulous profiteers, exceed the standard use of synthetic food coloring, and even use of the dye can not be used as a food additive, which seriously endanger the people of health.

"Sudan" is not a food additive, but a chemical dye. Its chemical composition contains a compound called naphthalene, the substance with the azo structure, due to the nature of this chemical structure determines its carcinogenicity, apparent toxic effects on the bodys liver and kidney organs. Sudan dyes are chemical dyes, is mainly used in petroleum, oil and other industrial solvents, the purpose is to make enriched, but also for the shoes, floors, graced.

Formaldehyde (HCHO), also known as ant aldehyde, colorless gas with a pungent irritating odor. Gas density of 1.067 kg / cubic meter, soluble in water and ethanol. Is gaseous at room temperature, usually in an aqueous solution form, is a strong fungicide, with the efficacy of antisepsis, sterilization and stability, the World Health Organization identified as carcinogenic and teratogenic substances. 35-40% formaldehyde solution, commonly known as formalin.

There carotene C40H56 (orange), lycopene C40H56O2 (red), carminic acid Na2S2O4 (red), Amaranth (purple), indigo C16H10N202 (blue), curcumin (yellow).