Rambutan

Rambutan (; Nephelium lappaceum) is a medium-sized tropical tree in the family Sapindaceae.

Description

It is an evergreen tree growing to a height of . The leaves are alternate, long, pinnate, with three to eleven leaflets, each leaflet wide and broad with an entire margin.

The flowers are small, , apetalous, discoidal, and borne in erect terminal panicles wide.

The fruit flesh, the aril, is translucent, whitish, or very pale pink, with a sweet, mildly acidic flavor reminiscent of grapes. Similarly, in Vietnam, they are called (meaning 'messy hair'). The Chinese name is (Mandarin hóngmáodān, Hokkien âng-mô͘-tan), literally 'red-haired pellet'.

Composition

thumb|right|A cluster of yellowish rambutan

Nutrients

Rambutan fruit is 78% water, 21% carbohydrates, 1% protein, and has negligible fat (see table; data are for canned fruit in syrup; raw fruit data are unpublished). In a reference amount of , the canned fruit supplies 82 calories and only manganese at 15% of the Daily Value (DV), while other micronutrients are in low content (less than 10% DV, table).

Phytochemicals

As an un-pigmented fruit flesh, rambutan does not contain significant polyphenol content, but its colorful rind displays diverse phenolic acids, such as syringic, coumaric, gallic, caffeic, and ellagic acids. Rambutan seeds contain equal proportions of saturated and unsaturated fatty acids, where arachidic (34%) and oleic (42%) acids, respectively, are the highest in fat content.

The pleasant fragrance of rambutan fruit derives from numerous volatile organic compounds, including beta-damascenone, vanillin, phenylacetic acid, and cinnamic acid.

Ecology

Pollination

Aromatic rambutan flowers are highly attractive to many insects, especially bees. Flies (Diptera), bees (Hymenoptera), and ants (Solenopsis) are the main pollinators. Among the Diptera, Lucilia spp. are abundant, and among the Hymenoptera, honey bees (Apis dorsata and A. cerana) and the stingless bee genus Trigona are the major visitors.

Varieties

Well over 200 cultivars were developed from selected clones available throughout tropical Asia. In Indonesia, 22 rambutan cultivars were identified as good quality, with five as leading commercial cultivars: 'Binjai', 'Lebak Bulus', 'Rapiah', 'Cimacan' and 'Sinyonya', with other popular cultivars including 'Simacan', 'Silengkeng', 'Sikonto' and 'Aceh kuning'. The trees grow well at elevations up to above sea level and do best in deep soil, clay loam, or sandy loam rich in organic matter. They grow on hilly terrain where there is good drainage.

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. The initial fruit set may approach 25 percent, but a high abortion level contributes to a much lower level of production at harvest (1 to 3 percent). The fruit matures 15 to 18 weeks after flowering.

Rambutan cultivation in Sri Lanka mainly consists of small home gardens. Malwana, a village in the Kelani River Valley, is popular for its rambutan orchards. Their production comes to market in 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 January and February in areas such as Bibile, Medagama, and Monaragala.

Both male and female flowers are faintly sweet-scented and have functional nectaries at the ovary base. Female flowers produce two to three times more nectar than male flowers. Nectar sugar concentration ranges between 18–47 percent and is similar between the flower types. Rambutans are an important nectar source for bees in Malaysia.

Cross-pollination is a necessity because the anther is absent in most functionally female flowers. Although apomixis may occur in some cultivars, rambutans, like lychee, are dependent upon insects for pollination. In Malaysia, where only about one percent of the female flowers set fruit, no fruit is set on bagged flowers while hand pollination resulted in a 13 percent fruit set. Pollinators may maintain 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.

Production

thumb|right|[[Javanese people|Javanese rambutan seller in Semarang, Indonesia]]

Rambutan is a fruit tree cultivated in humid tropical Southeast Asia. It is a common garden fruit tree and propagated commercially in small orchards. It is one of the best-known fruits of Southeast Asia and is also widely cultivated elsewhere in the tropics including Africa, southern Mexico, the Caribbean islands, Costa Rica, Honduras, Guatemala, Panama, India, Vietnam, Philippines, and Sri Lanka. In Java, the orchards and pekarangan (habitation yards) in the villages of Greater Jakarta and West Java have been known as rambutan production centers since the colonial era, with a trading center in Pasar Minggu, South Jakarta.

During 2017 and years before, imports of rambutan to the European Union were about 1,000 tonnes annually, enabling a year-round supply from numerous tropical suppliers.

The fruits are usually sold fresh and have a short shelf-life, as well as grown in the Pathanamthitta District of the southern state of Kerala.

Rambutans are not climacteric fruit—that is, they ripen only on the tree and appear not to produce a ripening agent, such as the plant hormone ethylene, after being harvested. In general, the fruit has a short shelf life in ambient conditions but implementing methods that can extend such is a productional advantage. Certain treatments like irradiation and the use of hot-forced air can help in fruit preservation although the former has seen more success.

Distribution

The center of genetic diversity for rambutans is the Indonesian region. It has spread from there to parts of Asia, Africa, Oceania, and Central America.

Gallery

File:Rambutan Muda.jpg|Young rambutan fruit in Malaysia

File:RambutanKuning.jpg|Ripe yellow rambutan fruit in Malaysia

File:LakeSampalocjf7542 08.JPG|Unripe rambutan fruits in the Philippines

File:Rambutan Binjai Pasar Baru Jakarta.JPG|'Rambutan Binjai', one of the leading cultivars in Indonesia

File:Three rambutan colors.jpg|Three colors of rambutan

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