Citrus Color and Flavor

Citrus fruits owe their yellow and orange colors (orange comes ultimately from the Sanskrit word for the fruit) to a complex mixture of carotenoids, only a small portion of which has vitamin A activity. The fruit peels start out green, and in the tropics often stay that way even when the fruit ripens. In other regions, cold temperatures trigger destruction of chlorophyll in the peel, and the carotenoids become visible. Fruits of commerce are often picked green and treated with ethylene to improve their color, and coated with an edible wax to slow moisture loss. Pink and red grapefruit are colored by lycopene, and red sweet oranges by a mixture of lycopene and beta-carotene and by cryptoxanthin. The purple-red of blood oranges comes from anthocyanins.