The grapefruit is a subtropical citrus tree grown for its bitter fruit, an 18th-century hybrid first bred in Jamaica. When found in Barbados it was named the "forbidden fruit"; it is also called the "shaddock", after its creator.
These evergreen trees are usually found at around 5–6 metres (16–20 ft) tall, although they can reach 13–15 metres (43–49 ft). The leaves are dark green, long (up to 150 mm, or 6 inches) and thin. It produces 5 cm (2 in) white four-petaled flowers. The fruit is yellow-orange skinned and largely oblate, and ranges in diameter from 10–15 cm. The flesh is segmented and acidic, varying in color depending on the cultivars, which include white, pink and red pulps of varying sweetness. The 1929 US Ruby Red (of the Redblush variety) has the first grapefruit patent.
The fruit has only become popular from the late 19th century; before that it was only grown as an ornamental plant. The US quickly became a major producer of the fruit, with orchards in Florida, Texas, Arizona, and California. In Spanish, the fruit is known as toronja or pomelo.
One ancestor was the Jamaican sweet orange (Citrus sinensis); the other was the Indonesian pomelo (Citrus maxima). Captain Shaddock brought pumelo seeds to Jamaica and bred the first fruit. It is closer to the orange.
The hybrid fruit was in 1750 documented by the Rev. Griffith Hughes describing specimens from Barbados. Currently, the grapefruit is said to be one of the "Seven Wonders of Barbados." It was brought to Florida by Count Odette Philippe in 1823 in what is now known as Safety Harbor. Further crosses have produced the tangelo (1905), the minneola (1931), and the sweetie (1984). The sweetie has very small genetic and other differences from pomelo.
The grapefruit was known as the shaddock or shattuck until the 1800s. Its current name alludes to clusters of the fruit on the tree, which often appear similar to grapes. Botanically, it was not distinguished from the pomelo until the 1830s, when it was given the name Citrus paradisi. Its true origins were not determined until the 1940s. This led to the official name being altered to Citrus × paradisi.
The 1929 Ruby Red patent was associated with real commercial success, which came after the discovery of a red grapefruit growing on a pink variety. Only with Ruby Red did the grapefruit transform into a real agricultural fruit. The Red grapefruit, starting from the Ruby Red, has even become a symbol fruit of Texas, where white "inferior" grapefruit were eliminated and only red grapefruit were grown for decades. Using radiation to trigger mutations, new varieties were developed to retain the red tones which typically faded to pink, with Rio Red is the current (2007) Texas grapefruit with registered trademarks Rio Star and Ruby-Sweet, also sometimes promoted as "Reddest" and "Texas Choice".
Grapefruit comes in many varieties, determinable by color, which is caused by the pigmentation of the fruit in respect of both its state of ripeness and genetic bent. The most popular varieties cultivated today are red, white, and pink hues, referring to the inside, pulp color of the fruit. The family of flavors range from highly acidic and somewhat bitter to sweet and tart. Grapefruit mercaptan, a sulfur-containing terpene, is one of the substances which has a strong influence on the taste and odor of grapefruit, compared with other citrus fruits.
In Costa Rica, especially in Atenas, grapefruits are often cooked to remove their sourness, rendering them as sweets; they are also stuffed with dulce de leche, resulting in a dessert called toronja rellena (stuffed grapefruit).
Grapefruit peel oil is used in aromatherapy and it is historically known for its aroma.
Grapefruit has also been investigated in cancer medicine pharmacodynamics. Although it inhibits the metabolism of some drugs, which is generally considered a bad thing, this allows some cancer drugs to be used at a lower dose, because of inhibited metabolism. This requires a smaller amount, which, in principle, can reduce the overall cost of an "effective" dose.
It also eases constipation, as it causes loosening of the bowels and stimulates defecation (especially true for pink grapefruit).
A grapefruit is cut in half, and the flesh can be sprinkled with a couple of teaspoons of 'household' sugar (optional), and left covered for an hour or two. The flesh is then eaten as normal.
This one is great when mixed with sochu (or Shochu). I had some of the best grapefruit sochu in Tokyo, especially after some bbq. If you've not tried it this way, you must when in Japan or in a Japanese restaurant!