| Brazil Nut Tree | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Asterids |
| Order: | Ericales |
| Family: | Lecythidaceae |
| Genus: | Bertholletia |
| Species: | B. excelsa |
| Binomial name | |
| Bertholletia excelsa Humb. & Bonpl. |
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The Brazil nut (Bertholletia excelsa) is a South American tree in the family Lecythidaceae, and also the name of the tree's commercially harvested edible seed.
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The Brazil nut family is in the order Ericales, as are other well known plants such as: blueberries, cranberries, sapote, gutta-percha, tea, kiwi fruit, phlox, and persimmons.
The Brazil nut tree is the only species in the monotypic type genus Bertholletia. It is native to the Guianas, Venezuela, Brazil, eastern Colombia, eastern Peru and eastern Bolivia. It occurs as scattered trees in large forests on the banks of the Amazon, Rio Negro, Tapajós, and the Orinoco. The genus is named after the French chemist Claude Louis Berthollet.
The Brazil nut is a large tree, reaching 50 metres (165 ft) tall and 1–2 metres (3–6.5 ft) trunk diameter, among the largest of trees in the Amazon Rainforests. It may live for 500 years or more, and according to some authorities often reaches an age of 1,000 years.[1] The stem is straight and commonly unbranched for well over half the tree's height, with a large emergent crown of long branches above the surrounding canopy of other trees.
The bark is grayish and smooth. The leaves are dry-season deciduous, alternate, simple, entire or crenate, oblong, 20–35 centimetre long and 10–15 centimetres broad. The flowers are small, greenish-white, in panicles 5–10 centimetres long; each flower has a two-parted, deciduous calyx, six unequal cream-colored petals, and numerous stamens united into a broad, hood-shaped mass.
Brazil nut trees produce fruit almost exclusively in pristine forests, as disturbed forests lack the large-body bees of the genera Bombus, Centris, Epicharis, Eulaema, and Xylocopa which are the only ones capable of pollinating the tree's flowers.[2][3] Brazil nuts have been harvested from plantations but production is low and it is currently not economically viable.[4][5][6]
The Brazil nut tree's yellow flowers contain very sweet nectar and can only be pollinated by an insect strong enough to lift the coiled hood on the flower and with a tongue long enough to negotiate the complex coiled flower. For this reason, the Brazil nut's reproduction depends on the presence of the orchid Coryanthes vasquezii,[7] which does not grow on the Brazil nut tree itself.[8] The orchids produce a scent that attracts small male long-tongued orchid bees (Euglossa spp), as the male bees need that scent to attract females. The large female long-tongued orchid bee pollinates the Brazil nut tree. Without the orchid, the bees do not mate, and therefore the lack of bees means the fruit does not get pollinated.
The fruit takes 14 months to mature after pollination of the flowers. The fruit itself is a large capsule 10–15 centimetres diameter resembling a coconut endocarp in size and weighing up to 2 kilograms. It has a hard, woody shell 8–12 millimetres thick, and inside contains 8–24 triangular seeds 4–5 centimetres long (the "Brazil nuts") packed like the segments of an orange; it is not a true nut in the botanical sense.
The capsule contains a small hole at one end, which enables large rodents like the Agouti to gnaw it open. They then eat some of the nuts inside while burying others for later use; some of these are able to germinate into new Brazil nut trees. Most of the seeds are "planted" by the Agoutis in shady places, and the young saplings may have to wait years, in a state of dormancy, for a tree to fall and sunlight to reach it. It is not until then that it starts growing again. Capuchin monkeys have been reported to open Brazil nuts using a stone as an anvil.
Despite their name, the most significant exporter of Brazil nuts is not Brazil but Bolivia, where they are called almendras. In Brazil these nuts are called castanhas-do-Pará (literally "nuts from Pará"), but Acreans call them castanhas-do-Acre instead. Indigenous names include juvia in the Orinoco area, and sapucaia in the rest of Brazil.
While cooks classify the Brazil nut as a nut, botanists consider it to be a seed and not a nut, because in nuts the shell splits in half with the meat separate from the shell.
Around 20,000 tons of Brazil nuts are harvested each year, of which Bolivia accounts for about 50%, Brazil 40% and Peru 10% (2000 estimates).[9] In 1980, annual production was around 40,000 tons per year from Brazil alone, and in 1970 Brazil harvested a reported 104,487 tons of nuts.[10]
Brazil nuts for international trade come entirely from wild collection rather than from plantations. This has been advanced as a model for generating income from a tropical forest without destroying it. The nuts are gathered by migrant workers known as castanheiros.
Analysis of tree ages in areas that are harvested show that moderate and intense gathering takes so many seeds that not enough are left to replace older trees as they die. Sites with light gathering activities had many young trees, while sites with intense gathering practices had hardly any young trees.[11]
Statistical tests were done to determine what environmental factors could be contributing to the lack of younger trees. The most consistent effect was found to be the level of gathering activity at a particular site. A computer model predicting the size of trees where people picked all the nuts matched the tree size data that was gathered from physical sites that had heavy harvesting.
| Nutritional value per 100 g (3.5 oz) | |
|---|---|
| Energy | 2,743 kJ (656 kcal) |
| Carbohydrates | 12.27 g |
| - Starch | 0.25 g |
| - Sugars | 2.33 g |
| - Dietary fiber | 7.5 g |
| Fat | 66.43 g |
| Protein | 14.32 g |
| - Tryptophan | 0.141 g |
| - Threonine | 0.362 g |
| - Isoleucine | 0.516 g |
| - Leucine | 1.155 g |
| - Lysine | 0.492 g |
| - Methionine | 1.008 g |
| - Cystine | 0.367 g |
| - Phenylalanine | 0.630 g |
| - Tyrosine | 0.420 g |
| - Valine | 0.756 g |
| - Arginine | 2.148 g |
| - Histidine | 0.386 g |
| - Alanine | 0.577 g |
| - Aspartic acid | 1.346 g |
| - Glutamic acid | 3.147 g |
| - Glycine | 0.718 g |
| - Proline | 0.657 g |
| - Serine | 0.683 g |
| Water | 3.48 g |
| Thiamine (vit. B1) | 0.617 mg (54%) |
| Riboflavin (vit. B2) | 0.035 mg (3%) |
| Niacin (vit. B3) | 0.295 mg (2%) |
| Vitamin B6 | 0.101 mg (8%) |
| Folate (vit. B9) | 22 μg (6%) |
| Vitamin C | 0.7 mg (1%) |
| Vitamin E | 5.73 mg (38%) |
| Calcium | 160 mg (16%) |
| Iron | 2.43 mg (19%) |
| Magnesium | 376 mg (106%) |
| Manganese | 1.223 mg (58%) |
| Phosphorus | 725 mg (104%) |
| Potassium | 659 mg (14%) |
| Sodium | 3 mg (0%) |
| Zinc | 4.06 mg (43%) |
| Percentages are relative to US recommendations for adults. Source: USDA Nutrient Database |
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Brazil nuts are 18% protein by weight, 13% carbohydrates, and 69% fat. 91% of its calories come from fat. The fat breakdown is roughly 25% saturated, 41% monounsaturated, and 34% polyunsaturated.[12] The saturated fat content of Brazil nuts is among the highest of all nuts, surpassing macadamia nuts, which are primarily monounsaturated fat,[13] and the nuts are pressed for their oil. Because of the resulting rich taste, Brazil nuts can often substitute for macadamia nuts or even coconut in recipes. Also due to their high polyunsaturated fat content, primarily omega-6, shelled Brazil nuts soon become rancid.
Nutritionally, Brazil nuts are a good source of some vitamins and minerals. A cup or 133 grams of Brazil nuts contains the vitamins thiamin (0.8 mg—55% DV) and vitamin E (7.6 mg—38% DV); minerals calcium (213 mg—21% DV), magnesium (500 mg—125% DV), phosphorus (946 mg—96% DV), copper (2.3 mg—116% DV), and manganese (1.6 mg—81%),[14] and are perhaps the richest dietary source of selenium; one ounce can contain as much as 10 times the adult USRDA (U.S. Recommended Dietary Allowances), more even than the Tolerable Upper Intake Level (UL), although the amount of selenium within batches of nuts varies greatly.[15][16]
Recent research suggests that proper selenium intake is correlated with a reduced risk of both breast cancer and prostate cancer.[17] This has led some health commentators and nutritionists to recommend the consumption of Brazil nuts as a protective measure.[18][19] These findings are inconclusive, however; other investigations into the effects of selenium on prostate cancer were inconclusive.[20]
Brazil nuts have one of the highest concentrations of phytic acid at 2 to 6% of dry weight. (Phytic acid can prevent absorption of some nutrients, mainly iron, but is also a subject of research and possibly confers health benefits - see phytic acid article for more information.)
Despite the possible health benefits of the nut, the European Union has imposed strict regulations on the import from Brazil of Brazil nuts in their shells, as the shells have been found to contain high levels of aflatoxins, which can lead to liver cancer.[21]
Brazil nuts contain small amounts of radium. Although the amount of radium, a radioactive element, is very small, about 1–7 pCi/g (40–260 Bq/kg), and most of it is not retained by the body, this is 1,000 times higher than in other foods. According to Oak Ridge Associated Universities, this is not because of elevated levels of radium in the soil, but due to "the very extensive root system of the tree."[22]
As well as its food use, Brazil nut oil is also used as a lubricant in clocks, for making artists' paints, and in the cosmetics industry.
The lumber from Brazil nut trees (not to be confused with Brazilwood) is of excellent quality, but logging the trees is prohibited by law in all three producing countries (Brazil, Bolivia and Peru). Illegal extraction of timber and land clearances present a continuing threat.[23]
The Brazil nut effect is the tendency of the larger items to rise to the top of a mixture of items of various sizes but similar densities, e.g., Brazil nuts mixed with peanuts.