Carambola

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 5–6). When cut in cross-section, it resembles a star, giving it the name of star fruit. The entire fruit is edible, usually raw, and may be cooked or made into relishes, preserves, garnish, and juices. It is commonly consumed 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 cultivated throughout tropical areas of the world.

Carambola fruits contain oxalic acid and the neurotoxin caramboxin. Consuming large quantities of the fruit, especially for individuals with some types of kidney disease, can result in serious adverse health effects.

The center of diversity and the original range of Averrhoa carambola is tropical Southeast Asia, where it has been cultivated for centuries. It was introduced to the Indian Subcontinent and Sri Lanka by Austronesian traders, along with ancient Austronesian cultigens like langsat, noni, and santol. They remain common in those areas and in East Asia and throughout Oceania and the Pacific Islands. They are cultivated commercially in India, Southeast Asia, southern China, Taiwan, and the southern United States. They are also grown in Central America, South America, and the U.S. state of Hawaii, the Caribbean, and parts of Africa. They are grown as ornamentals. Carambola is considered to be at risk of becoming an invasive species in many world regions.

The carambola tree has a short trunk with many branches, reaching up to 9 m (30 ft) in height. Its deciduous leaves are 15–25 cm (6–10 in) long, with 5 to 11 ovate leaflets medium-green in color. Flowers are lilac in color, with purple streaks, and are about 5 mm (1⁄4 in) wide.

The showy fruits have a thin, waxy pericarp, orange-yellow skin, and crisp, yellow flesh with juice when ripe. The fruit is about 5 to 15 cm (2 to 6 in) in length and is an oval shape. It usually has five or six prominent longitudinal ridges. In cross-section, it resembles a star. The flesh is translucent and light yellow to yellow in color. Each fruit can have 10 to 12 flat, light brown seeds about 5–15 mm (1⁄4–1⁄2 in) in width and enclosed in gelatinous aril. Once removed from the fruit, they lose viability within a few days.

Like the closely related bilimbi, there are two main types of carambola: the small sour (or tart) type and the larger sweet type. The sour varieties have a higher oxalic acid content than the sweet type. Several cultivars have been developed in recent years. The most common cultivars grown commercially include the sweet types "Arkin" (Florida), "Yang Tao" (Taiwan), "Ma fueng" (Thailand), "Maha" (Malaysia), and "Demak" (Indonesia) and the sour types "Golden Star", "Newcomb", "Star King", and "Thayer" (all from Florida). Some sour varieties, like "Golden Star", can become sweet if allowed to ripen.

Carambola is known by many names across its regions of cultivation, including 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.

The entire fruit is edible, including the slightly waxy skin. The flesh is crunchy, firm, and extremely juicy. It does not contain fibers and has a texture similar in consistency to that of grapes. Carambolas are best consumed shortly after they ripen, when they are yellow with a light shade of green, or just after all traces of green have disappeared. They will also have brown ridges at the edges and feel firm. Fruits picked while still slightly green will turn yellow in storage at room temperature, but will not increase in sugar content. Overripe carambola will be yellow with brown spots and can become blander in taste and soggier in consistency.