Carambola

The name "starfruit" can also refer to a marsh plant, Damasonium. This article is about the fruit. For other uses of the name, see Carambola (disambiguation).

Carambola, also known as star fruit, is the fruit of Averrhoa carambola, a species of tree native to tropical Southeast Asia. The edible fruit has distinctive ridges running down its sides, usually five or six. When it is cut across, it looks like a star, which is how it got the name star fruit.

The whole fruit can be eaten, usually raw. It may also be cooked or made into relishes, preserves, garnish, and juices. People commonly eat it in Southeast Asia, South Asia, the South Pacific, Micronesia, parts of East Asia, the United States, parts of Latin America, and the Caribbean. The tree is grown in tropical areas all over the world.

Carambola fruits contain oxalic acid and the poison caramboxin, which affects the nerves. Eating large amounts of the fruit can cause serious health problems, especially for people with some types of kidney disease.

Origins and distribution

Main article: Averrhoa carambola

The center of diversity and the original range of Averrhoa carambola is tropical Southeast Asia, where it has been grown for centuries. Austronesian traders brought it to the Indian subcontinent and Sri Lanka, along with other old plants like langsat, noni, and santol. These fruits are still common in those areas, in East Asia, and across Oceania and the Pacific Islands.

They are grown commercially in India, Southeast Asia, southern China, Taiwan, and the southern United States. They also grow in Central America, South America, the US state of Hawaii, the Caribbean, and parts of Africa. Some people grow them as ornamentals. In many parts of the world, carambola is considered at risk of becoming an invasive species.

Description

The carambola tree has a short trunk with many branches and can grow up to 9 m (30 ft) tall. Its leaves are 15–25 cm (6–10 in) long and have 5–11 medium-green leaflets. The lilac flowers have purple streaks and are about 5 mm (1⁄4 in) wide.

The fruit has a thin, orange-yellow skin and crisp, juicy yellow flesh when ripe. It is about 5–15 cm (2–6 in) long, oval in shape, and usually has five or six ridges running down its sides. When cut across, it looks like a star. Each fruit holds 10–12 flat, light brown seeds. Once removed from the fruit, the seeds lose their ability to grow within a few days. There are two main kinds: small sour types and larger sweet types. Some sour kinds, like "Golden Star", become sweet if left to ripen.

Common names

The carambola goes by many names in the places where it is grown. For example, it is called khế in Vietnam, balimbing in the Philippines, belimbing in Indonesia and Malaysia, ma fen in China, kamaranga in India, and carambolo in Spanish-speaking countries.

Culinary

The whole fruit can be eaten, including the slightly waxy skin. The flesh is crunchy, firm, and very juicy. It has no fibers and feels a bit like grapes. Carambolas taste best soon after they ripen, when they are yellow with a light shade of green, or just after all the green is gone. They will have brown ridges at the edges and feel firm. Fruit picked while still slightly green will turn yellow in storage at room temperature, but it will not gain sugar. Overripe carambola is yellow with brown spots and can taste blander and feel softer.

Ripe sweet carambolas are sweet without being overwhelming, with rarely more than 4% sugar, and they have a tart, sour undertone. Their taste has been compared to a mix of apple, pear, grape, and citrus family fruits. Unripe star fruits are firmer and sour, like green apples. In Southeast Asia, ripe carambolas are usually stewed in cloves and sugar, sometimes with apples, and in China they are cooked with fish. Unripe sour carambolas are mixed with other chopped spices to make relishes in Australia, and in the Philippines they are eaten dipped in rock salt. The juice is used in iced drinks, especially from sour varieties. Raw carambola is 91% water, 7% carbohydrates, and 1% protein, with almost no fat (see table). A 100-gram serving gives 128 kilojoules (31 kilocalories) of food energy and is rich in vitamin C, at 41% of the Daily Value. It has no other micronutrients in significant amounts (see table).

Health risks

Carambolas contain caramboxin and oxalic acid, which are both harmful to people with long-term kidney disease (including kidney failure), kidney stones, or those who are having kidney dialysis treatment. When people with kidney failure eat carambola, it can cause nerve damage. Symptoms can include hiccups, vomiting, nausea, mental confusion, coma, and sometimes death. Caramboxin is a neurotoxin, which means it can harm nerves. It is similar in structure to phenylalanine and acts as a glutamatergic agonist.

Like the grapefruit, carambola is considered a strong inhibitor of seven cytochrome P450 isoforms. These enzymes play an important part in the first-pass elimination of many medicines. Because of this, eating carambola or drinking its juice with certain prescription medicines can greatly increase how much of the medicine stays in the body.

Cultivation

Carambola is a tropical and subtropical fruit that can grow at heights up to 1,200 m (4,000 ft). It likes full sun and needs humid air and at least 1,800 mm (70 in) of rain each year. It can grow in many soil types, as long as the soil drains well. Heavy rains can stop the tree from making fruit. Trees are planted at least 6 m (20 ft) apart and are usually fed fertilizer three times a year. They grow quickly and usually start making fruit when they are four or five years old. In ideal conditions, one tree can produce 90 to 180 kilograms (200 to 400 pounds) of fruit a year. The tree flowers all year, but in South Florida it can also fruit at other times.

Major pests of carambola include carambola fruit flies, fruit moths, ants, and birds. Crops can also be damaged by frost. Many countries grow carambola for sale, including Australia, Guyana, India, Israel, Malaysia, the Philippines, Taiwan, and the US. Malaysia is a leader in producing star fruit and sells it to Asia and Europe. However, whole star fruits cannot yet be brought into the US from Malaysia under United States Department of Agriculture rules. In the United States, carambolas grow in warm areas, including parts of Florida and Hawaii. The fruit became popular in the US in the 1970s, thanks to backyard horticulturalist Morris Arkin in Coral Gables, Florida.

In popular culture

The trees are also grown as decorations for their colorful, unusually shaped fruits, their dark green leaves, and their lavender to pink flowers. The juice of the more sour types can be used to clean rusty or tarnished metal, especially brass, and to bleach rust stains from cloth. It may also be used as a mordant in dyeing.

In the farming video game Stardew Valley, players can grow carambola, which is called "starfruit" in the game. It is one of the most valuable crops. The game's icon wrongly shows the fruit looking like its real cross-section, and it shows the plant as a crop that is harvested only once instead of a tree. In the Philippines, the Filipino word for starfruit, balimbing, has come to mean a turncoat, which is someone who changes political sides for their own benefit rather than because of their beliefs.