Dragon fruit, or pitaya, is instantly recognizable by its vibrant, scaled pink rind and often equally colorful interior. This intense pink or magenta hue is the result of specific plant chemistry. The vivid color of this tropical cactus fruit comes from a class of pigments called betalains. These compounds are responsible for the fruit’s appearance.
The Pigment Responsible for the Hue
The color of the dragon fruit’s flesh and skin is provided by betalains, which are nitrogen-containing, water-soluble pigments. Within this class, the red-to-violet shades are attributed to betacyanins, the dominant pigment in red-fleshed varieties like Hylocereus costaricensis. The concentration of these betacyanins, particularly compounds like betanin, dictates the depth of the pink or magenta color.
The plant manufactures these pigments through a biosynthetic pathway that begins with the amino acid tyrosine. This process creates the betalain structure, which is stored in the vacuoles of the plant cells. While these colors help attract pollinators and seed dispersers, betalains also serve a biological role by offering protection to the plant. They act as antioxidants and provide photoprotection, shielding the plant’s tissues from intense sunlight and UV radiation.
How Betalains Differ from Common Plant Colors
Betalains represent an alternative coloring system, chemically distinct from the more common red and purple pigments found in most fruits and flowers. Most red, purple, and blue hues in nature, such as those in blueberries or apples, are due to anthocyanins. The structural difference is that betalains incorporate nitrogen into their molecular framework, while anthocyanins do not.
Plants rarely produce both pigment classes, meaning they are mutually exclusive in nature. This chemical difference also impacts how the color behaves; betalains are stable across a wider pH range (between 3 and 7) compared to anthocyanins. This stability is a factor in the dragon fruit’s color. The unique chemistry of betalains distinguishes the fruit from those colored by anthocyanins.
Why Some Dragon Fruit is White
Not all dragon fruit varieties exhibit pink flesh; some, such as the Hylocereus undatus species, are known for their white interior despite having a pink or red rind. This difference in internal color is a matter of genetics and pigment distribution. White-fleshed varieties possess a genetic makeup that limits or prevents the synthesis and accumulation of betacyanins in the edible inner pulp.
In white varieties, pigment production is largely confined to the fruit’s outer peel, which still displays a deep pink hue. Conversely, red-fleshed types, like Hylocereus costaricensis, have the genetic programming to deposit a high concentration of betacyanins throughout the flesh. Variations in color intensity, from pale pink to deep magenta, are a reflection of the varying concentration of betacyanin pigments produced by different cultivars.