Star fruit (carambola)

Star fruit, also known as carambola, is a star shaped tropical fruit with sweet and sour flavor. Carambola is native to Malayan peninsula and cultivated in many parts of Southeast Asia, Pacific islands and China for its fruits. Although abundant and plentiful, carambola is yet to gain popularity, especially in the western world.

Scientific name: Averrhoa carambola. The genus averrhoa includes two well-known sorrel (Oxalidaceae) families of fruiting trees, carambola and bilimbi (tree cucumber).

The fruit is recognized as belimbing manis in many South East Asian regions and kamrakh in India.

Star fruit is a small, bushy evergreen tree that grows very well under hot, humid, tropical conditions. The plant bears small lilac colored, bell-shaped flowers in clusters which subsequently develop into oblong shaped fruits with characteristic five angled edges (sides or ribs) that appear like a starfish in cross sections. Both sweet and sour varieties begin to yield under cultivable orchards, and ready for harvesting when the plants reach about 3-4 years old.

Carambola fruit features light-green to yellow with attractive smooth waxy surface and weighs about 70-130g. Inside, its crispy, juicy pulp can either be mildly sweet or extremely sour depending upon the cultivar type and amount of oxalic acid concentration. In some seed types, 2-5 tiny edible seeds found at the center of each angled cavitiy.

Health benefits of star fruit

• Star fruit is one of very low calorie exotic fruits. 100 g fruit just provides 31 calories, which is much lower than for any other popular tropical fruits. Nonetheless, it has an impressive list of essential nutrients, antioxidants, and vitamins required for well-being.
• The fruit along with its waxy peel provides a good amount of dietary fiber. Fiber helps prevent absorption of dietary LDL cholesterol in the gut. The dietary fibers also help protect the mucous membrane of the colon from exposure to toxic substances by binding to cancer-causing chemicals in the colon.
• Star fruit contains good quantities of vitamin-C. Vitamin C is a powerful natural antioxidant. 100 g of fresh fruit provides 34.7 mg or 57% of daily-required levels of vitamin C. In general, consumption of fruits rich in vitamin C helps the human body develop resistance against infectious agents and scavenge harmful, pro-inflammatory free radicals from the body.
• Star fruit is rich in antioxidant phyto-nutrient polyphenolic flavonoids. Some of the important flavonoids present are quercetin, epicatechin, and gallic acid. Total polyphenol contents (Folin assay) in this fruit is 143 mg/100 g. Altogether, these compounds help protect from deleterious effects of oxygen derived free radicals by warding them off the body.
• In addition, it is a good source of B-complex vitamins such as folates, riboflavin, and pyridoxine (vitamin B-6). Together, these vitamins help as co-factors for enzymes in metabolism as well as in various synthetic functions inside the body.
• It also carry small amount of minerals and electrolytes like potassium, phosphorus, and zinc and iron. Potassium is an important component of cell and body fluids helps controlling heart rate and blood pressure; thus, it counters bad influences of sodium.

Medicinal uses

• Star fruit and its juice is often recommended in many folk medicine in Brazil as a diuretic (to increase urine output), expectorant, and to suppress cough. (Medical disclaimer).

Selection and Storage

Fresh star fruits can be available twice in a season. In Florida, for example, Arkin cultivars are available from December to March. In general, fruits just short of ripening stage are picked up for shipment and storage; since the ripe fruits tend to bruise easily, especially their thin ribbed edges.

While buying, choose uniform, large, attractive looking, yellow-orange fruits. Avoid green, small size fruits since they tend to be extremely acidic, and unappetizing. Avoid those with cuts, bruise, shriveled or spots.

Ripe fruits tend to perish early; however, they stay well in cold storages when kept at appropriate temperatures. At home, unripe light green fruits may be kept at room temperature until they turn rich orange-yellow color. Ripe fruits may keep well for 2-3 days at room temperature, but required to be stored inside the refrigerator for extended shelf life.

Preparation and Serving tips

Star fruits are generally used as a garnish in salads, sorbets, drinks, as well as to impart tart flavor in dishes.

Given their high oxalic acid content and extreme tartness, they used quite less frequently in food the industry.

To prepare, wash them thoroughly in cold water, dry mop using absorbent cloth. Trim off the ends and dry edges of the ribbed angles. Cut the fruit crossway into thin sections, which resemble like a starfish. Pick out any seeds located near its center.

Here are some serving tips:

• Only sweet variety carambola can be eaten fresh, or mixed with other fruits in salads. Fresh fruit can also be juiced and used in cocktails with other complementing tropical fruit juices.
• Sour type fruits are favored in cooking as they impart unique tart flavor to poultry, meat, and seafood dishes.
• Cut sections of fresh fruit added in stews, curries, and stir-fries with chicken, and fish and shrimp.
• The fruit can be used to make sauce, pickle, chutney, tarts, and jam.

Safety profile

Star fruit is one of the plant sources that contain highest concentration of oxalic acid; 100 g of fresh fruit contains 50,000-95,800 ppm of oxalic acid. Oxalic acid has been considered as anti-nutrient compound as it interferes with absorption and metabolism of several natural minerals such as calcium, magnesium, etc. It also predisposes to a condition known as oxaluria, a condition which may leads to the formation of oxalate kidney stones. In some people with impaired kidney function, its consumption would result in renal failure and may cause death. People with known kidney disease should therefore, advice to avoid eating star fruit.

Further, Star fruit, like grapefruit, has been found to interact adversely with many drugs. Some of the compounds in carambola irreversibly inhibit cytochrome P450 3A4 isoenzymes (3A4) in the intestines and liver. This resulting increase in drug levels leads to adverse effects and/or toxicity. It is therefore, strongly advised to consult your healthcare practitioner before eating star fruit or its products if taking any kind of pharmaceutical drugs.