Brazil nut
Brazil nut trees,
reaching a height of 160 feet, tower above the forest
canopy in the Amazon rainforest of Brazil, Bolivia
and Peru. The nuts grow inside coconut-sized shells
that weigh about five pounds each and contain 15 to
25 nuts. Only the agouti -- a large rodent with long
legs, a large rump and a humped back -- have teeth
sharp and strong enough to gnaw open the nut's tough
outer shell and yank out the seeds. Nuts missed by
the agoutis are collected by castañeros, local
people who harvest some 40,000 tons of nuts a year.
Locally, the oil is used for cooking, in lamps and
in soaps, but most Brazil nuts are dried, graded,
and shelled before being packed in vacuum-sealed bags
for shipment to the West. US Consumers alone eat $17
million worth of Brazil nuts each year.
Nutritional value and taste
Brazil nuts are
an excellent source of selenium and a good source
of magnesium and thiamine. They are 14% protein, 11%
carbohydrates, and 67% fat. The fat breakdown is roughly
25% saturated, 41% monounsaturated, and 34% polyunsaturated.
The saturated fat content of Brazil nuts is among
the highest of all nuts, surpassing even macadamia
nuts. Because of the resulting rich taste, Brazil
nuts can often substitute for macadamia nuts or even
coconuts in recipes. The high fat content of the nuts
results in their not keeping well, and particularly,
shelled Brazil nuts soon become rancid. The nuts are
also pressed for oil; as well as for food use, Brazil
nut oil is also used as a lubricant in clocks and
for making artists' paints.
The Tree
Image
credit
Brazil Nuts come from a South American
tree Bertholletia excelsa in the family Lecythidaceae.
It is the only species in the genus Bertholletia.
It is native to Guiana, 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, and the Orinoco. It is a large
tree, reaching 30–45 m tall and 1–2 m
trunk diameter, among the largest of trees in the
Amazon Rainforests. It may live for 500 years or more.
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.
Pollination
Brazil nuts only produce fruit in
virgin forests, as forests that are not virgin usually
lack an orchid that is indirectly responsible for
the pollination of the flowers. The orchids produce
a scent that attracts male bees, as the male bees
need that scent to attract females. Without the orchid,
the bees cannot mate, and therefore the lack of bees
means the fruit do not get pollinated. If both the
orchids and the bees are present, the fruit takes
14 months to mature after pollination of the flowers,
and is a large capsule 10–15 cm diameter resembling
a coconut endocarp in size and weighing up to 2 kg.
It has a hard, woody shell 8–12 mm thick, and
inside contains 8–24 triangular seeds 4–5
cm long (Brazil nuts) packed like the segments of
an orange; it is not a true nut in the botanical sense.
The capsule and the Agouti
Image
credit
The capsule contains a small hole
at one end, which enables large rodents like the Agouti
to gnaw open the capsule. They then eat some of the
nuts inside while burying others for later use; some
of these are able to germinate to produce 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. If a Brazil
Nut fruit strikes a person on the head, minor to severe
head trauma, can be expected, the severity varying
with the fruit's weight.
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 "chestnuts
from Pará", but Acreans call them castanhas-do-Acre
instead. Indigenous names include juvia in the Orinoco
area, and sapucaia in Brazil.
Effects of harvesting
Brazil nuts for international trade come entirely
from wild collection rather than from farms. This
has been touted as a model for generating income from
a tropical forest without destroying it.
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.
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.
The Brazil Nut Effect
The Brazil nut effect, where large
items mixed with other smaller items (e.g. Brazil
nuts mixed with peanuts) tend to rise to the top,
is named after the species' large nuts.
Read
more about this here.
Image sources:
upper left---The Food Museum collection; upper
right: lower
right; lower
left
Brazil
nut website
The
ecologically important Brazil nut harvest
Brazil
nut harvest threatened
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