Lycopene the structure of the molecule was determined by 1931. In its natural, all-"trans" form, the molecule is long and straight, constrained by its system of 11 conjugated double bonds. Each extension in this conjugated system reduces the energy required for electrons to transition to higher energy states, allowing the molecule to absorb visible light of progressively longer wavelengths. Lycopene absorbs all but the longest wavelengths of visible light, so it appears red. Plants and photosynthetic bacteria naturally produce all-"trans" lycopene. When exposed to light or heat, lycopene can undergo isomerization to any of a number of "cis"-isomers, which have a
Lycopene two terminal isoprene groups of lycopene can be cyclized to produce beta-carotene, which can then be transformed into a wide variety of xanthophylls. Lycopene is the pigment in tomato-containing sauces, turning plastic cookware orange, and is insoluble in water. It can be dissolved only in organic solvents and oils. Because of its nonpolarity, lycopene in food preparations will stain any sufficiently porous material, including most plastics. To remove this staining, the plastics can be soaked in a solution containing a small amount of household bleach. Absorption of lycopene requires that it be combined with bile salts and fat to form