main ingredient in marmalade. Sour-orange
flowers are used to make orange flower water.
Grapefruit The grapefruit originated as a
hybrid of the sweet orange and pummelo in
the Caribbean in the 18th century, and is still
mainly grown in the Americas. The red types
owe their color to lycopene, and first appeared
as chance mutations in Florida and in Texas
early in the 20th century (the more recent and
popular Star Ruby and Rio Red varieties were
created by intentionally inducing mutations
with radiation). Unlike the anthocyanin
coloration of blood oranges, grapefruit
lycopene requires consistent high growing
temperatures to develop well, appears evenly
through all the juice vesicles, and is stable to
heat. The characteristic moderate bitterness is
caused by a phenolic substance called
naringin, whose concentration declines as the
fruit ripens. Like navel oranges, grapefruits
also contain a precursor of limonin, and its