A food company imported 5 tons of Chili powder from India in 2002, and used it to produce various brands of Worcester seasonings, which were used by many food vendors or restaurants downstream. Later, the British Food Standards Agency found out that this pepper contained carcinogens, so it was wanted. The Sudan Red incident also kicked off.
Extended data:
Chemical principle
Sudan red substance contains nitrogen-nitrogen double bond (azo group), that is, -N=N- in the structural formula, and forms a chromophore together with benzene rings connected at both ends. Azobenzene yoke system composed of azo groups and aromatic structures can absorb visible light with a certain wavelength, so substances containing azobenzene system can show a certain color.
Azo bond absorbs photons to produce two transition forms: π-π * transition in double bond (maximum absorption wavelength is 3 18 nm) and n-π transition (energy difference is lower than the former, maximum absorption wavelength is 443 nm). At the same time, due to the action of electron-repelling groups, the electron cloud density shifts to azo groups, and new absorption appears, which can show different colors. Because the wavelength range of visible light is 380 nm ~ 780 nm, azo dyes can show almost all kinds of colors.
The benzene ring, naphthalene ring, phenolic hydroxyl group and methyl group in Sudan red molecule belong to electron exclusion groups, which makes the electron density transfer to azo group larger, so the absorbed light wave is longer and the color is orange-red.
Azo group is a double bond, so azo dye has certain oxidation, which can undergo addition reaction and then be reduced to colorless amine. The reduction products of Sudan red are aniline and naphthylamine, so it has carcinogenic effect on animals.