According to popular belief and the origin of its name, rambutan is native to Indonesia and Malaysia. The earliest record of rambutan trees show that they were cultivated by the Malayan jungle tribes around their temporary settlements, a practice followed to date. Rambutan trees grow naturally in Thailand, Vietnam, the Philippines, and elsewhere in Southeast Asia, although its precise natural distribution is unknown. It is closely related to several other edible tropical fruits including the lychee, longan, and mamoncillo. It is native to the Indonesian Archipelago, from where it spread westwards to Thailand, Burma, Sri Lanka and India; northwards to Vietnam, and the Philippines.
A species regularly sold in Costa Rican markets may be known as "wild" rambutan. Yellow in color, it is smaller than the usual red variety. The flesh exposed when the outer skin is peeled off is sweet and sour, slightly grape-like and gummy to the taste. In Panama and Costa Rican Spanish, it is known as mamón chino ("Chinese Sucker") due to its Asian origin and the likeness of the edible part with Melicoccus bijugatus. The fruit has been successfully transplanted by grafting in Puerto Rico.
Rambutans are a non-climacteric fruit—that is, they ripen only on the tree.
It is an evergreen tree growing to a height of 12–20 m. The leaves are alternate, 10–30 cm long, pinnate, with 3–11 leaflets, each leaflet 5–15 cm wide and 3–10 cm broad, with an entire margin. The flowers are small, 2.5–5 mm, apetalous, discoidal, and borne in erect terminal panicles 15–30 cm wide.
Rambutan trees are either male (producing only staminate flowers and, hence, produce no fruit), female (producing flowers that are only functionally female), or hermaphroditic (producing flowers that are female with a small percentage of male flowers).
The fruit is a round to oval drupe 3–6 cm (rarely to 8 cm) tall and 3–4 cm broad, borne in a loose pendant cluster of 10–20 together. The leathery skin is reddish (rarely orange or yellow), and covered with fleshy pliable spines, hence the name rambutan, derived from the Malay word rambut, which means hairs. The fruit flesh is translucent, whitish or very pale pink, with a sweet, mildly acidic flavor very reminiscent of grapes.
The single seed is glossy brown, 1–1.3 cm, with a white basal scar. Soft and crunchy, the seeds may be cooked and eaten. Some folklore regards the seeds as poisonous, but tests of seed extracts reveal no toxicity to mice, even in doses up to 2500 mg/kg. The extract does show some analgesic activity, however. The peeled fruits can be cooked and eaten, first the grape-like aril, then the nutty seed, with no waste.
Cultivation
Rambutan is adapted to warm tropical climates, around 22–30°, and is sensitive to temperatures below 10 °C. It is grown commercially within 12–15° of the equator. The tree grows well on heights up to 500 metres (1,600 ft) above sea-level and does best in deep soil; clay loam or sandy loam rich in organic matter, and thrive on hilly terrain as they require good drainage. Rambutan is propagated by grafting, air-layering, and budding; the latter is most common as trees grown from seed often produce sour fruit. Budded trees may fruit after 2–3 years with optimum production occurring after 8–10 years. Trees grown from seed bear after 5–6 years.
In some areas rambutan trees can bear fruit twice annually, once in late fall and early winter with a shorter season in late spring and early summer. In other areas like Costa Rica there is a single fruit season, with the start of the rainy season in April stimulating flowering and the fruit is usually ripe in August and September. The fragile nutritious fruit must ripen on the tree, then they are harvested over a four- to seven-week period. The fresh fruit are easily bruised and have a limited shelf life. An average tree may produce 5,000–6,000 or more fruit (60–70 kg or 130–155 lb per tree). Yields begin at 1.2 tonnes per hectare (0.5 tons/acre) in young orchards and may reach 20 tonnes per hectare (8 tons per acre) on mature trees. In Hawaii, 24 of 38 cultivated hectares (60 of 95 acres) were harvested producing 120 tonnes of fruit in 1997. It has been suggested that yields could be increased via improved orchard management, including pollination, and by planting high yielding compact cultivars.
Most commercial cultivars are hermaphroditic; cultivars that produce only functionally female flowers require the presence of male trees. Male trees are seldom found as vegetative selection has favored hermaphroditic clones that produce a high proportion of functionally female flowers and a much lower number of flowers that produce pollen. There are over 3,000 greenish-white flowers in male panicles, each with 5–7 anthers and a non-functional ovary. Male flowers have yellow nectaries and 5–7 stamens. There are about 500 greenish-yellow flowers in each hermaphroditic panicle. Each flower has six anthers, usually a bi-lobed stigma, and one ovule in each of its two sections (locules). The flowers are receptive for about one day but may persist if pollinators are excluded.
In Thailand, rambutan trees were first planted in Surat Thani in 1926 by the Chinese Malay K. Vong in Ban Na San. An annual rambutan fair is held during August harvest time.
In Malaysia, rambutan flowers from March to July and again between June and November, usually in response to rain following a dry period. Flowering periods differ for other localities. Most, but not all, flowers open early in the day. Up to 100 flowers in each female panicle may be open each day during peak bloom. Initial fruit set may approach 25% but a high level of abortion level contributes to a much lower level of production at harvest (1 to 3%). The fruit matures 15–18 weeks after flowering.
Rambutan cultivation in Sri Lanka mainly consists of small home gardens. Malwana, a village located in the Kelani River Valley, is popular for its rambutan orchards. Their production comes to market in the months of May, June and July, when it is very common to observe seasonal traders along the streets of Colombo. Sri Lanka also has some off-season rambutan production in the months of January and February in areas like Bibile, Medagama and Monaragala.
Both male and female flowers are faintly sweet scented and have functional nectaries at the ovary base. Female flowers produce 2–3 times more nectar than male flowers. Nectar sugar concentration ranges between 18% and 47% and is similar between the flower types. Rambutan is an important nectar source for bees in Malaysia.
Cross-pollination is a necessity because anther is absent in most functionally female flowers. Although apomixis may occur in some cultivars, research has shown that rambutan, like lychee, is dependent upon insects for pollination. In Malaysia, where only about one percent of the female flowers set fruit, research revealed that no fruit is set on bagged flowers while hand pollination resulted in 13 percent fruit set. These studies further suggest that pollinators may maintain a fidelity to either male or hermaphroditic flowers (trees), thus limiting pollination and fruit set under natural conditions where crossing between male and female flowers is required.
Advantage of Rambutan
This fruit is a traditional medicine in Malaysia and Indonesia that is being used for hundreds of years. It is used in a number of treatments which includes diabetes, hypertension and various other ailments.
The carbohydrates and protein content of rambutan help to increase energy and prevent bloating. Rambutan is also rich in water which helps to get back the lost energy and quenches thirst.
Vitamin C in Rambutan helps in the absorption of minerals, iron and copper. It also protects the body from getting damaged from free radicals.
One of the main compounds of rambutan is Gallic acid. This compound behaves like a free radical scavenger that protects our body from oxidative damage and is particularly helpful to fight cancer.
This fruit contains moderate amounts of copper which is necessary for the creation of white and red blood cells. It also contains manganese which our body needs to produce and activate enzymes.
Phosphorus in rambutan helps to remove the waste in kidneys and is essential for the development, repair, and maintenance of tissues and body cells. Rambutan also contains significant amounts of Calcium which works together with phosphorus to fortify the teeth and strengthens bones.
Rambutans are an excellent source of iron which helps to correct the amount of oxygen in the body which controls dizziness and fatigue due to anaemia, an illness caused by iron deficiency.
Rambutan has good fiber content and is low in calories. The fruit keeps us full for a long time due to its high fiber and water content and controls irregular hunger pangs. This also aids in weight reduction.
Rambutan is also good for treating common illnesses like headache, thrush and dysentery. For headache, the leaves are used as a poultice on the temples. This calms the nerves and reduces headache. A decoction of the bark is applied on the tongue to treat thrush. A decoction of roots is used to lower fever.
The other health benefits of Rambutan is in its antiseptic qualities. It helps to fight the body infection which invades our body.
Besides nutritional benefits, rambutan also offers therapeutic functions. Consuming the fruit can help to kill intestinal parasites and helps to relieve symptoms of diarrhoea and fever.
Rambutan fruit is rich in sugar, mostly fructose and sucrose, but less calories, only around 60 in a fruit. Rambutan fruit is abundant with vitamin C and has potassium, iron, beta carotene or vitamin A, and a little calcium, magnesium zinc, sodium, niacin, fiber and protein.
The fruit has been employed in traditional medicine in Malaysia and Indonesia for hundreds of years as a treatment for diabetes, hypertension and various ailments. Besides the antioxidants obtained in its beta carotene and vitamin C, research workers at the Chiang Mai University in Thailand found that the rambutan pulp, seeds and skin have strong, plant based, antioxidants called flavonoids. Certain kinds of flavonoids are believed to reduce cholesterol and possess anti-cancerous, anti-inflammatory attributes.
One of many organic compounds contained in the skin is Gallic acid. This compound behaves like a free radical scavenger as it helps protect against oxidative damage in our body and is regarded as a strong aid in the battle against cancer. Due to its extensive antioxidant activity, compared to other exotic fruits like pomegranate, rambutan skin extract may be promoted as a drug or health supplement product.
The rambutan is abundant with vitamin C. 10-12 rambutans provide 75-90 mg ascorbic acid, more than double the amount recommended to take daily. An essential antioxidant, vitamin C prevents body cells from being damaged by free radicals and helps the absorption of iron.
The fruit also has small quantities of copper, necessary for the creation of white and red blood cells, and also manganese, which our body needs to produce and activate some enzymes.
A single serving of rambutan functions as an excellent iron source. The iron in what you eat promotes the correct amount of oxygen inside you, which help stop the dizziness and fatigue due to anemia, an illness caused by low iron.
Additionally, you will obtain 4.3% of the daily recommended intake of phosphorus when you have a serving of rambutan. Phosphorus helps remove waste in your kidneys and is essential for the development, repair and maintenance of tissues and body cells. Rambutan also has a small amount of calcium; both phosphorus and calcium work together to fortify your teeth and bones.
Besides nutritional benefits, rambutan also has therapeutic functions. Consuming the fruit can help kill intestinal parasites, while help relieve symptoms of diarrhea. Some traditional healers in Malaysia also employ parts of the fruit to cure fever. Talk to your doctor before using rambutan as remedy for any ailment.
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