Rambutan by R.Borgacci

What are

Rambutans are small edible fruits with a characteristic shape produced by a tropical tree botanically framed as Nephelium lappaceum (Sapindaceae family).

This plant, homonymous in the common language, is native to Southeast Tropical Asia - more precisely from the Malay-Indonesian region - and seems to be closely related to other plants known as litchi (Sapindaceae Family, Genus Litchi and specie chinensis ), longan (Family Sapindaceae, Genus Dimocarpus and logan species) and mamoncillo (Family Sapindaceae, Genus Melincoccus and bijugatus species).

Curiosity

The name rambutan derives from the Malay-Indonesian word "rambut", which means "hair" - a clear reference to the numerous hairy protuberances of the fruit - combined with the constructive suffix of the name "-an". For the same reason, in Vietnam it is called "chôm chôm" - which means "filthy hair".

Rambutans are therefore foods of vegetable origin. From a nutritional point of view, they use a considerable concentration of water, soluble / simple sugars - which, in the context of the fruits, outline a significant caloric intake - minerals and vitamins - such as manganese and ascorbic acid - and very few fibers. The rambutan fruit is in effect a member of the VII fundamental group of foods - fruit and vegetables rich in vitamin C.

The rambutans can be eaten raw or included in some recipes, typical of the autochthonous areas of the fruit, rather than in other parts of the world where it arrives thanks to the trade routes.

Nutritional Properties

Nutritional properties of rambutans

The fruits of rambutan do not have excellent nutritional properties. They contain different nutrients but in modest quantities. They have more relevance in the VII fundamental group of foods, even if the share of vitamin C is not so high.

Rambutans, unlike lychees and grapes - to which, once peeled, they might resemble - are instead poor in antioxidant polyphenols. Note : the pleasant fragrance of the pulp derives from numerous volatile organic compounds, including beta-damascenone, vanillin, phenylacetic acid and cinnamic acid.

Did you know that ...

The peel, considered inedible, seems rich in phenolic acids, such as syringic, coumaric, gallic, caffeic and ellagic acids - with significant antioxidant activity in vitro.

Furthermore, the edible rambutan seeds contain equal percentages of saturated and unsaturated fatty acids - arachic acid (34%) and oleic acid (42%).

The pulp (arillo) of rambutan has a good water content and a caloric intake which, in the context of sweet fruits, can be considered medium-high. Energy is mainly supplied by carbohydrates, followed by irrelevant percentages of proteins and lipids. Carbohydrates are soluble and more precisely consisting of fructose. The few peptides have a low biological value and the fatty acid composition is in favor of the unsaturated ones.

The pulp of rambutan is free of cholesterol, gluten, lactose and histamine. The purine content should be very low, as well as that of phenylalanine.

As far as minerals are concerned, rambutan arils do not seem to have particularly important concentrations; the only exception is manganese; potassium is not abundant but it is still relevant. The levels of vitamin C (ascorbic acid) and vitamin PP (niacin) are more significant, but they are not amazing.

Diet

Rambutan in the diet

The pulp of rambutan lends itself to most diets. They are indicated in the diet against overweight and metabolic pathologies, as long as the portion is adequate. In particular, it may be necessary to reduce the quantity and frequency of consumption in the treatment of severe obesity; moreover, given the glycemic load is not entirely negligible, it is natural to wonder if the consumption could be suitable for the diet for type 2 diabetes mellitus and hypertriglyceridemia.

The rambutan aril has no contraindications in the treatment of arterial hypertension, hypercholesterolemia and hyperuricemia. The same applies to food intolerance to lactose, gluten and histamine. Despite being poor in purines, this food, containing a lot of fructose, when taken in large quantities can compromise the disposal of uric acid in the body, worsening the hyperuricemia and the formation of kidney stones of the same substrate. It is not contraindicated in phenylketonuria.

The abundance of water and the presence of potassium make the pulp of rambutan foods useful in the sportsman's diet. The fiber content, although not amazing, contributes to the achievement of the quota necessary to maintain intestinal health. The richness in vitamin C and polyphenols can be very useful to support the defensive action against free radicals. Furthermore, ascorbic acid is a necessary factor for the synthesis of collagen, a protein widespread in the human body, and contributes to supporting the immune system. The richness in manganese ensures the correct development of enzymatic activation and the metal-enzymatic constitution of various biological catalysts.

Kitchen

Rambutan in the kitchen

The pulp - or aril - is eaten mainly from rambutans. This, excellent fresh and raw, can also be used for the production of jams, jellies or canned fruit in syrup.

In most rambutan cultivars, the aril contains a seed, although the types that do not have it - freestone - are perhaps the most requested. Rambutans usually contain only one, light brown. This is rich in certain fats and oils - mainly oleic acid and arachic acid - precious for the industry and used in cooking - frying - and in soap making.

The roots, bark and leaves of Rambutan have various uses in traditional medicine and in the production of dyes.

Description

Description of rambutans

That of rambutan is an evergreen tree 12 to 20 m high. The leaves are alternate, 5-15 cm long and 3-10 cm broad, 10-30 cm apart, pinnate with regular margin. The flowers are small, 2.5-5 mm, apetallic, discoid and grouped into terminal panicles, 15-30 cm wide.

The rambutan plants can be male - they have only stemmed flowers and therefore they do not produce fruits - or females - they produce flowers that are only potentially female - or hermaphrodites - they produce female flowers with a small percentage of male flowers.

Description of rambutan fruits

The fruit is a single-seeded berry, 3-6 cm long - rarely up to 8 cm - and 3-4 cm wide; it has 10-20 elements in hanging clusters. The skin is leathery, reddish and rarely orange or yellow, covered with protuberances similar to "fleshy" and flexible thorns - from which, as we have seen, the origin of the name. The pulp of the fruit, actually formed from the aril, is translucent pink, whitish or very pale, with a sweet taste, slightly acidic and very similar to grapes - as, for that matter, also the fruit of the litchi to which it resembles a lot, especially peeled.

The seed is single, round or oval, 1-1.3 cm long, glossy brown and with a white basal line. It has a soft consistency and contains saturated and unsaturated fats in equal measure.

Did you know that ...

If properly cooked, the seeds of rambutan fruit can also be eaten.

Production

Where does the rambutan tree come from?

Native to tropical Southeast Asia, the rambutan plant is normally cultivated in various countries of this region. From there it spread to other parts of Asia, Africa, Oceania and Central America. The widest variety of cultivars, wild and cultivated, is found in Indonesia and Malaysia.

Between the 13th and 15th centuries, Arab merchants - who played an important role in the Indian Ocean trading network - introduced rambutan to Zanzibar and Pemba, in East Africa. Some plantations have also been developed in different parts of India. In the nineteenth century the Dutch introduced the Rambutans from their colony in Southeast Asia to Suriname, in South America. Subsequently, the plant was also exported to the tropical Americas, the coastal plains of Colombia, Ecuador, Honduras, Costa Rica, Trinidad and Cuba.

In 1906 there was an attempt to introduce rambutan in the South-Eastern United States, using seeds imported from Java, but the operation failed in all the affected areas except for Puerto Rico. In 1912, rambutan was introduced from Indonesia to the Philippines. Further inputs followed in various countries, from Indonesia in 1920 and from Malaysia in 1930, but until the 1950s the distribution of the rambutan tree could be considered limited.

Notes on the pollination of the rambutan tree

The fragrant rambutan flowers are much sought after by insects, especially bees. Flies ( Diptera ), bees ( Hymenoptera ) and ants ( Solenopsis ) are the main pollinators. Among the Diptera there is an abundance of Lucilia and among the Hymenoptera honey bees ( Apis dorsata and A. cerana ) and the Trigona genus. The colonies of A. cerana that feed on rambutan flowers produce large quantities of honey. The bees that look for the nectar usually settle on the stigma of the male flowers and collect significant quantities of pollen; little pollen has been seen on bees that draw on female flowers. Although the male flowers blossom at 06:00, the action of A. cerana is more intense between 07:00 and 11:00, decreasing later. In Thailand, A. cerana is the preferred species for pollination of small-scale rambutans.

Tree cultivation

Rambutan is suitable for tropical climates, around 22-30 ° C, and is sensitive to temperatures below 10 ° C. It is grown within 12-15 ° by the equator. The tree grows well at altitudes up to 500 m above sea level, it adapts better to deep, clayey or rich in organic matter soils, and thrives on hilly terrain as it requires good drainage. Rambutan is propagated by grafting, ramming and budding; the latter is the least widespread, as the trees grown from seeds often produce more acid fruits. Trees can bear fruit after 2-3 years, with optimal production after 8-10 years. Those grown from seeds start after five or six years.

In some areas, rambutan trees can bear fruit twice a year, one in late autumn and early winter, the other - shorter - in late spring and early summer. Other areas, such as Costa Rica, have a single fruiting season, with flowering stimulation in April - rainy season - and ripening in August and September. The fruits must ripen on the tree and are harvested over a period of four to seven weeks. The fresh fruits are delicate to bruise and have a limited conservation. An average tree can produce 5000-6000 or more fruits - 60-70 kg per tree. The crops start with 1.2 tons per hectare in young orchards and can reach 20 tons per hectare in mature ones. In 1997, in Hawaii, 24 out of 38 cultivated hectares produced 120 tons of fruit. Yields could be increased by improving orchard management, including pollination, and by planting compact high yield cultivars.

Most commercial cultivars are hermaphrodite; those that produce only functionally feminine flowers require the presence of male trees. Male trees are rarely found, as vegetative selection has favored hermaphrodite clones that produce a high percentage of functionally female flowers and a much lower number of pollen-producing flowers. The male plants produce over 3000 greenish-white flowers and the hermaphrodite ones only 500 - greenish-yellow color. The concentration of sugar in the nectar varies between 18-47% and is similar among the types of flowers. Rambutan is an important source of nectar for bees in Malaysia.

During the flowering peak, up to 100 flowers can be opened each female cob every day. The transformation into fruit can approach 25%, but the high level of abortion contributes to a much lower level of production - from 1 to 3%. The fruit ripens 15-18 weeks after flowering.

Cultivar of rambutan

Over 200 cultivars have been developed from selected clones available throughout tropical Asia. Most are selected for compact growth, facilitating harvesting.

In Indonesia, 22 Rambutan cultivars have been identified, of which the main ones are five: Binjai, Lebak Bulus, Rapiah, Cimacan and Sinyonya. In Malaysia, the commercial varieties are: Chooi Ang, Peng Thing Bee, Ya Tow, Azimat and Ayer Mas.

The fruit of the Maharlika Rambutan has the characteristic of allowing the seed and the aril to be easily separated.

Producing countries

Rambutan has a fairly important fruit production throughout tropical Southeast Asia, especially in Indonesia, Malaysia and Thailand; crops are widespread especially in small orchards. The rambutan fruits, among the most popular of the original areas, are now widely cultivated in the tropics, including Africa, the Caribbean islands, Costa Rica, Honduras, Panama, India, the Philippines and Sri Lanka. In Ecuador on the island of Puerto Rico it is known as Achotillo.

In 2005, Thailand was the largest rambutan producer in the world, with 588, 000 tons a year (55.5%), followed by Indonesia with 320, 000 tons (30.2%) and Malaysia with 126, 300 tons (11.9% ); the three countries together represent 97% of the world rambutan supply. In Thailand, the most important rambutan cultivation center is located in Surat Thani province. In Indonesia, the production center is located in the western part, which includes Java, Sumatra and Kalimantan. In Java, it is located in the villages of Greater Jakarta and in the west. Production is increasing in Australia and, in 1997, was one of the three main tropical fruits produced in Hawaii.

The fruits are usually sold fresh and are used to prepare jams and jellies or canned. Trees also have a particular ornamental-landscape role.

In India, these fruits are mostly imported from Thailand and grown mainly in the Pathanamthitta district, in the southern state of Kerala.

deepening

Like carambola, rambutans are not climacteric fruits - that is, they ripen only on the tree - therefore, after harvesting, they do not appear to produce the ethylene ripening agent. As it cannot be harvested unripe, the availability of fresh rambutans in the European market is therefore quite limited.