Pigments

Plant pigments have widely different chemical structures. The major chemical types are chlorophylls, carotenoids, anthocyanins, and betalains. The intensity of color is due to both the pigment concentrations in the fruit and their location within the fruit. Anthocyanins and carotenoids are antioxidants with potential health benefits to humans. Fruit extracts rich in them can be found in health stores in pill form.

The major pigment of fruit is chlorophyll, and the color of all green plant parts is due to this pigment. Carotenoids are lipophylic pigments that provide most of the yellow colors in nature, as also some red and orange. Most black, red, orange, blue, and purple coloration of fruit is due to the hydrophylic anthocyanins, glycosides of antho-cyanidins. There are six major anthocyanidins (Figure F2.1), differing in substitution of the two rings, but most temperate fruit contain different glycosides of cyanidin. Another category of chemicals, which functionally and chemically replace anthocyanins in the Chen-opodiflorae (including cacti and beets), is betalains (betacyanins and betaxanthins). Their presence results in plant colors similar to antho-cyanins, but they have a totally different structure and biosynthetic origin. They do not occur in any temperate tree fruit.

FIGURE F2.1. Anthocyanidins. The six most common are pelargonidin R"=H, R"=H; cyanidin, R'=OH, R"=H; peonidin R'=OMe, R"=H; delphinidin R'=OH, R"=OH; petunidin R'=OMe, R"=OH; and malvidin R'=OMe, R"=OMe.
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