Carambola

Carambola, or starfruit, is the fruit of Averrhoa carambola, a species of tree native to the Philippines (where they are called balimbing or saranate, depending on their sourness), Indonesia, India and Sri Lanka. The tree and its fruit are popular throughout Southeast Asia, the South Pacific and parts of East Asia. The tree is also cultivated throughout the tropics, such as in Peru, Colombia, Trinidad, Ecuador, Guyana, Dominican Republic and Brazil, and, in the United States, in south Florida and Hawaii. The carambola should not be confused with the closely related bilimbi, which is also called belimbing in Indonesia.
The fruit has ridges running down its sides (usually five) which in cross-section resembles a star, hence its name. The number of ridges can vary from three to six.
Origins and distribution
The carambola has been grown in parts of Asia for hundreds of years — it may have originated in Sri Lanka or Moluccas, Indonesia. Malaysia is the global leader in starfruit production by volume and ships the product all over Asia and Europe.
Due to concerns on pests and pathogens, however, whole starfruits cannot yet be imported to the US from Malaysia under current FDA/USDA regulation. In the United States, starfruits are grown in tropical and semitropical areas, including Florida, Puerto Rico and Hawaii.
Gastronomy
The fruit is entirely edible, including the slightly waxy skin. The flesh is crunchy, firm, and extremely juicy. The texture is similar in consistency to grapes.
Carambolas are best consumed when ripe, when they are yellow with a light shade of green. They will also have brown ridges at the five edges and feel firm. Overripe starfruit will be yellow with brown spots and can become soggier in consistency.
Ripe carambolas are sweet without being overwhelming, and has a tart, sour undertone. The taste is difficult to compare, but it has been likened to a mix of apple, pear and citrus family fruits all at once. Unripe starfruits are firmer, sour, and taste like green apples.

Health
Benefits
Carambola is rich in antioxidants and vitamin C and low in sugar, sodium and acid. It is also a potent source of both primary and secondary polyphenolic antioxidants. A. carambola has both antioxidant and antimicrobial activities: scavenging of NO by the fruit extract is dependent on concentration and stage of ripening. Extracts showed antimicrobial activity against E. coli, Salmonella typhi, Staphylococcus aureus and Bacillus cereus
Risks
Carambola is a fairly complex fruit with many benefits, but like strawberries, a small percentage of the human population should be cautious of the fruit for health reasons. Like the grapefruit, carambola contains oxalic acid, which can be harmful to individuals suffering from kidney failure, kidney stones, or those under kidney dialysis treatment. Consumption by those with kidney failure can produce hiccups, vomiting, nausea, and mental confusion. Fatal outcomes have been documented in some patients.
Drug interactions
Like the grapefruit, carambola is considered to be a potent inhibitor of seven cytochrome P450 isoforms. These enzymes are significant in the first-pass elimination of many medicines, and thus, the consumption of carambola or its juice in combination with certain medications can significantly increase their effective dosage within the body. Research into grapefruit juice has identified a number of common medications affected, including statins, which are commonly used to treat cardiovascular illness, and benzodiazepines (a tranquilizer family including diazepam).
Cultivation
The carambola is a tropical and subtropical fruit. In India, it is called kamrak, and can be grown at up to 4,000 feet (1,200 m) in elevation. It prefers full sun exposure, but requires enough humidity and a total of 70 inches or more of rainfall a year. It does not have a soil type preference, but it requires good drainage.
Carambola trees are planted at least 20 feet (6.1 m) from each other and typically are fertilized three times a year. The tree grows rapidly and typically produces fruit at four or five years of age. The large amount of rain during spring actually reduces the amount of fruit, but, in ideal conditions, carambola can produce from 200 to 400 pounds (91 to 180 kg) of fruit a year. The fruit is harvested mainly during the months of June, July, and August, but sometimes year-round.
Major pests are fruit flies, ants, and birds. Crops are also susceptible to frosts, especially in the United States.