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Cashew
(Anacardium occidentale)
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PLANT
IMAGES
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Family: Anacardiaceae
Genus:
Species: Anacardium
Synonyms:
Common names: Cashew,
Parts Used: Seeds, Leaves, Bark
| Cashew |
| HERBAL PROPERTIES AND ACTIONS |
| Main Actions |
Other Actions |
Standard Dosage |
| treats diarrhea |
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Bark tea |
| antimicrobial |
anti-inflamatory |
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| astringent |
diuretic |
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| hypoglycemic |
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Fruit juice: daily |
| warts |
ring worms |
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| botflies |
treats skin infections |
caustic shell oil: externally |
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A small to medium tree, generally single-trunked and
spreading in habit, up to 40' in height but generally 10-20' in
cultivation. In older trees, spread may be greater than
height, with lower limbs bending to touch the ground. Leaves are thick,
prominently veined, oval to spatulate in shape, with blunt tips and
entire margins. New foliage contains reddish pigment
CURRENT PRACTICAL USES
Every part of the cashew tree can be used: the root is a cleanser (purgative) while the light, water resistant bark is used to make canoes; the antibiotic property of the fruit juice, which is also rich in vitamin C, cures symptoms of the common cold, sore throat, flu and dysentery; the fruit itself treats premature aging of the skin and the nut alleviates cough, hiccup, depression and lowers blood cholesterol; the gum from the fruit stems is a natural repellent against insects and ants while the oil in the shell of the nut is used commercially for varnish, paints, shampoos and conditioners. Furthermore the medicinal properties of cashew have been evident against diabetes, tumors, and kidney problems.
Specific indications and Uses.—Post-partum and
other uterine hemorrhage, with profuse flow, cold extremities,
and pallid surface; haematuria; haemoptysis.
ORIGIN, HISTORY OF CULTIVATION
Cashew is native to northeastern Brazil, in the area
between the Atlantic rain forest and the Amazon rainforest. The
vegetation type of the region is dry forest, savannah woodland or thorn
scrub, and includes the almost desert-like Caatinga. Cashew is
sometimes referred to as a rainforest species and the nuts are found in
products that have a rainforest friendly label or connotation. Although
the trees will grow in tropical wet forests, they rarely produce many
nuts, and production is far greater in areas with a distinct wet and
dry season, such as its native range in Brazil, India and east Africa.
The Portuguese introduced cashew to the west coast
of India and east Africa in the 16th century, shortly after its
discovery in 1578. It was planted in India initially to reduce erosion,
and uses for the nut and pseudofruit, the cashew apple, were developed
much later. The trees were well adapted to the region, and became
naturalized. Trees also became naturalized in Central America and the
Caribbean islands. Nut domestication predated the arrival of
Europeans to Brazil, although international nut trade did not occur
until the 1920s. Native South Americans discovered that roasting nuts
in fire would remove the caustic oil, allowing the nut to be cracked
and consumed without any ill effects. The roasting practice was either
not known or not appreciated outside the native range, and as a result
the cashew apple was the first product consumed, with the nut being
discarded. Natives also knew of many medicinal uses for the apple
juice, bark, and caustic seed oil that were later exploited by
Europeans.
India developed more refined methods for removing
the caustic shell oil, and this country is given credit for developing
the modern nut industry. India led the world in cashew production for
many years until just recently, when production in Viet Nam surged
about 3-fold in a few years. In its native Brazil, cashew nut
production ranks in the top 5 of the world, and virtually all cashew
apples and juice products come from this country. Preliminary data
indicate the cashew nut production surpassed almond in 2003, and thus
cashew now claims the title of #1 nut crop in the world.
FOLKLORE, MEDICINAL PROPERTIES, NON-FOOD USAGE
Medicinal uses of cashew bark, leaves, and apple
juice are plentiful, and were well known prior to recorded
history in the native region of Brazil. Bark teas were used for
diarrhea, and the caustic shell oil was used to treat skin infections,
warts, worms, and botfly larvae beneath the skin. Teas and fruit juices
are known to have antimicrobial, anti-inflammatory, astringent,
diuretic, hypoglycemic, and other medicinal properties. The active
principles are thought to be tannins, anacardic acid, and cardol. The
red apples have higher tannin content than the yellow. Modern uses of
shell oil and fruit juice include facial peels and scalp conditioners
and shampoos. Clinical studies have documented the anti-inflammatory
properties of tannins, and the antimicrobial properties of anacardic
acid against several species, including Escherichia coli and Helicobacter pylori. Leaf extracts
show hypoglycemic activity in rodents, and a reduction in artificially
induced diabetes. Cashew apples contain up to 5 times the amount of
vitamin C as citrus and strawberries, and higher amounts of some
minerals than other fruits.
Cashew nut shell liquid (CNSL) is sandwiched in a
honeycomb layer of tissue between the two walls of the nut shell.
Industrial uses include automobile brakes, adhesives, paints and
varnishes, insecticides, electrical insulation, and anti-microbials.
The shell oil is highly caustic, causing moderate to severe skin
irritation. When wood is burned or nuts roasted, contact with or
breathing of the fumes can cause skin and eye irritation, inflammation,
and poisoning. In addition to CNSL, resins and gums from fruit stems or
bark is used as a varnish for books, wood, and flooring to protect from
ants and other home-invading insects.
The nut shell has an inner and outer wall, separated
by a honeycomb tissue infused with caustic oil. Cracking the nuts fresh
results in the oil contaminating the kernel, so nuts are roasted to
drive off oils before they are shelled. The nuts are about 22-30%
kernel by weight, and kernels are difficult to extract whole compared
to other tree nuts.
Soils and Climate
Cashews are said to be tolerant of sandy, poor soils
where many other crops will not thrive. Soil pH is generally on the
acidic side, 4.5-6.5. Trees are strongly taprooted and
drought tolerant if soils are deep, and can grow in areas receiving
only 30-50" of rain per year. Cashews are especially intolerant of poor
soil drainage.
Climatically, cashews prefer hot, tropical lowlands
(< 3000 ft elevation) with a distinct dry season. High rainfall and
humidity favor diseases that destroy the flowers and reduce fruit set.
They have no cold tolerance whatsoever, requiring protection from cold
even in extreme southern Florida.
Propagation
Propagation is most often by seed, planted directly
in the field where the tree is to be sited. Improved cashews are
propagated by grafting, layering, or cuttings. Fruit production occurs
in 4-5 yr from seed, and 2-3 yr from vegetative propagation.
Rootstocks
- generally none, but cashew seedlings can be used for rootstocks for
grafted trees.
Planting Design,
Training, Pruning
Cashews are planted at various densities, depending
on the intensity of production, amount of rainfall, and other factors.
New plantings are often established with 20-35 ft between trees and
rows. Higher densities are possible, but require selective tree
thinning as canopies enlarge. In arid Tanzania, research showed that
when about 50-60% of the ground area was covered by cashew tree canopy,
yield per acre was maximized. This is a relatively low amount of light
interception compared to intensive orchards, and probably reflects the
need for trees to explore large soil volumes in arid areas.
Cashews form open, spreading canopies naturally, and
very little information on pruning exists.
HARVEST, POSTHARVEST HANDLING
Maturity
The cashew apple and nut abscise from trees
naturally when ripe. Maturation occurs over a period of several weeks
during the dry season.
Harvest Method
Nuts are collected from the ground by hand. Frequent
passes though the planting must be made if apples are to be utilized,
as they are highly perishable. Rain at harvest may increase rot and
stimulate nut germination.
Postharvest
Handling
The presence of caustic cashew nut shell liquid
(CNSL) in the shells makes cashew processing more difficult and
hazardous than for other nut crops. After harvest, the nuts are dried
in the sun or in simple tray driers and stored for processing later.
Dried nuts can be stored for about 2 years at room temperature after
reaching water contents of 5-10%. Nuts are re-hydrated partially by
soaking or storing in high humidity since this facilitates extraction
of whole kernels and CNSL. Nuts are separated by size before roasting
to ensure uniformity of the roasting process.
Nuts are roasted in one of two ways: heating in pans
or drums over fire, or in hot oil. Heating in pans is done in small
scale operations. About 2 pounds of nuts are placed in a shallow, broad
pan much like a wok, which is heated over a fire. The CNSL exuded from
the shells ignites, and the nuts are stirred while they flame and smoke
for about 2 minutes. The smoke and flame is dowsed with water, and nuts
removed from the pan to dry. Drum roasters are semi-mechanized forms of
pan roasting, where nuts are fed into the high end of a large metal,
rotating drum that is tilted from horizontal. The nuts catch fire
during their transit along the drum and are sprayed with water at the
low end where they exit the drum. The hot oil methods are the most
sophisticated and generally reserved for larger processing facilities.
Nuts are immersed in a tank of CNSL heated to 375°F, and CNSL is
driven out of the shell, increasing the volume of hot oil in the tank.
About 50% of the oil is removed in 1-4 minutes, which is enough to
allow safe cracking of nuts. Roasting in hot oil is the only method
that captures CNSL as a by-product of cashew production.
After roasting, nuts are shelled either by hand or
in machines. Hand shelling uses wooden mallets to crack nuts, which is
very slow and tedious (only a few nuts per minute). However, cracking
employs a large number of people in poor, rural areas where cashews are
grown. Machine cracking can increase efficiency to a few dozen to 1000
kg of nuts per hour, but is used in only sophisticated operations.
Machines either use knives to open shells, or centrifugal force to
throw nuts against a hard surface. Hand cracking yields high numbers of
whole kernels, but whole kernel yields from machines vary from 20-75%.
Kernels are then dried in the sun or ovens at 160°F until the
moisture content is about 3%. The papery seed coat must be removed from
the nut, usually by hand at rates of up to about 25 lbs per day. Nuts
are graded by hand, and separated into whole kernels and various sized
pieces of broken kernels. Nuts are vacuum packed or packed in carbon
dioxide for export.
Cashew apples can be juiced easily since they do not
contain seed, however, juicing must be done immediately at harvest.
Apples yield about 60-70% of their weight as juice. Poor flavors, due
to tannins and oils, can be removed by steam treatment, cooking in
brine, or adding gelatin to juice with subsequent filtration (tannins
are precipitated by gelatin, as in wine). Juice can be concentrated and
frozen, or sulfited and stored at room temperature for several weeks.
Juice has properties allowing it to be fermented to wine easily; Feni
is a distilled beverage of about 40% alcohol content made from cashew
wine distillation.
Storage
Vacuum packed, roasted nuts can be stored for up to
one year, and carbon dioxide packing extends life an additional year.
The cashew apple may be consumed fresh, but contains
high quantities of tannins yielding a bitter taste and dry mouth feel.
It is more often cooked, partially dried, or candied, as in the
Dominican Republic and India. The alcoholic drink, Feni, is made from
fermented cashew apple juice in India. The wine made from the juice is
said to be the finest made from tropical fruits.
Per capita consumption of cashew is unknown, but
that of all tree nuts is 2.7 lbs/year in the USA. Cashews are likely to
be less than 1 lb/year.
Dietary value, per 100 gram edible portion
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Cashew nut
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Cashew apple |
| Water (%) |
3-7
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86
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| Calories |
578
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| Protein (%) |
18-22
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0.1
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Fat (%)
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46
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0.3
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Carbohydrates (%)
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27
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9-15
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Crude Fiber (%)
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1.1
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0.75
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% of US RDA* |
| Vitamin A |
0
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0
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| Thiamin, B1 |
45
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Riboflavin, B2
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12
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| Niacin |
12
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| Vitamin C |
0
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200-600
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| Calcium |
0.2
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0.5
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Phosphorus
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5.8
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2
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| Iron |
50
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5
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| Sodium |
4.6
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<0.1
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| Potassium |
12
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0.1
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* Percent of recommended daily allowance set by FDA, assuming a 154 lb
male adult, 2700 calories per day.
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