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The cashew tree (''Anacardium occidentale'') is a tropical evergreen tree native to South America in the genus '' Anacardium'' that produces the cashew seed and the cashew apple accessory fruit. The tree can grow as tall as , but the dwarf cultivars, growing up to , prove more profitable, with earlier maturity and greater yields. The cashew seed is commonly considered a
snack A snack is a small portion of food generally eaten between meals. Snacks come in a variety of forms including packaged snack foods and other processed foods, as well as items made from fresh ingredients at home. Traditionally, snacks are p ...
nut Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds * Nut (hardware), fastener used with a bolt Nut or Nuts may also refer to: Arts, entertainment, and media Com ...
(cashew nut) eaten on its own, used in recipes, or processed into cashew cheese or cashew butter. Like the tree, the nut is often simply called a cashew. Cashew allergies are triggered by the proteins found in tree nuts, and cooking often does not remove or change these proteins. In 2019, four million tonnes of cashew nuts were produced globally, with
Ivory Coast Ivory Coast, also known as Côte d'Ivoire, officially the Republic of Côte d'Ivoire, is a country on the southern coast of West Africa. Its capital is Yamoussoukro, in the centre of the country, while its largest city and economic centre is ...
and India as the leading producers. As well as the nut and fruit, the plant has several other uses. The shell of the cashew seed yields derivatives that can be used in many applications including lubricants, waterproofing, paints, and, starting in World War II, arms production. The cashew apple is a light reddish to yellow fruit, whose pulp and juice can be processed into a sweet, astringent fruit drink or fermented and distilled into liquor.


Description

The cashew tree is large and evergreen, growing to tall, with a short, often irregularly shaped trunk. The
leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
are spirally arranged, leathery textured, elliptic to obovate, long and broad, with smooth margins. The flowers are produced in a
panicle A panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a panicle are of ...
or corymb up to long; each flower is small, pale green at first, then turning reddish, with five slender, acute
petal Petals are modified Leaf, leaves that surround the reproductive parts of flowers. They are often advertising coloration, brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''c ...
s long. The largest cashew tree in the world covers an area around and is located in Natal, Brazil. The fruit of the cashew tree is an accessory fruit (sometimes called a pseudocarp or false fruit). What appears to be the fruit is an oval or pear-shaped structure, a
hypocarpium This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary o ...
, that develops from the
pedicel Pedicle or pedicel may refer to: Human anatomy *Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures ...
and the receptacle of the cashew flower. Called the cashew apple, better known in Central America as , it ripens into a yellow or red structure about long. The true fruit of the cashew tree is a kidney– or boxing-glove–shaped
drupe In botany, a drupe (or stone fruit) is an indehiscent fruit in which an outer fleshy part (exocarp, or skin, and mesocarp, or flesh) surrounds a single shell (the ''pit'', ''stone'', or '' pyrena'') of hardened endocarp with a seed (''kernel'') ...
that grows at the end of the cashew apple. The drupe first develops on the tree and then the pedicel expands to become the cashew apple. The drupe becomes the true fruit, a single shell-encased seed, which is often considered a
nut Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds * Nut (hardware), fastener used with a bolt Nut or Nuts may also refer to: Arts, entertainment, and media Com ...
in the culinary sense. The seed is surrounded by a double shell that contains an allergenic
phenolic Phenolic is an adjective and a substantive (noun) that may apply to : * Phenol (or carbolic acid), a colorless crystalline solid and aromatic compound * Phenols, a class of chemical compounds that include phenol * Phenolic content in wine * Phenol ...
resin,
anacardic acid Anacardic acids are phenolic lipids, chemical compounds found in the shell of the cashew nut (''Anacardium occidentale''). An acid form of urushiol, they also cause an allergic skin rash on contact, known as urushiol-induced contact dermatitis. An ...
—which is a potent skin irritant chemically related to the better-known and also toxic allergenic oil urushiol, which is found in the related poison ivy and lacquer tree.


Etymology

The English name derives from the Portuguese name for the fruit of the cashew tree: (), also known as , which itself is from the Tupian word , literally meaning "nut that produces itself". The generic name ''Anacardium'' is composed of the Greek prefix ''ana-'' ( grc, ἀνά-, aná, up, upward, label=none), the Greek ''cardia'' ( grc, καρδία, kardía, heart, label=none), and the New Latin suffix . It possibly refers to the heart shape of the fruit, to "the top of the fruit stem" or to the seed. The word ''anacardium'' was earlier used to refer to '' Semecarpus anacardium'' (the marking nut tree) before Carl Linnaeus transferred it to the cashew; both plants are in the same family. The
epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...
''occidentale'' derives from the Western (or Occidental) world. The plant has diverse
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
s in various languages among its wide distribution range, including ''anacardier'' (
French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...
) with the fruit referred to as ''pomme de Cajou'', ' (), or ' (Portuguese).


Distribution and habitat

The species is native to Northeastern Brazil and Southeastern Venezuela, and later was distributed around the world in the 1500s by
Portuguese explorers Portuguese maritime exploration resulted in the numerous territories and maritime routes recorded by the Portuguese as a result of their intensive maritime journeys during the 15th and 16th centuries. Portuguese sailors were at the vanguard of Eu ...
. Portuguese colonists in Brazil began exporting cashew nuts as early as the 1550s. The Portuguese took it to Goa, India between 1560 and 1565. From there, it spread throughout Southeast Asia and eventually Africa.


Cultivation

In 2014, rapid growth of cashew cultivation in
Ivory Coast Ivory Coast, also known as Côte d'Ivoire, officially the Republic of Côte d'Ivoire, is a country on the southern coast of West Africa. Its capital is Yamoussoukro, in the centre of the country, while its largest city and economic centre is ...
made this country the top African exporter. Fluctuations in world market prices, poor working conditions, and low pay for local harvesting have caused discontent in the cashew nut industry. The cashew tree is cultivated in the tropics between 25°N and 25°S, and is well-adapted to hot lowland areas with a pronounced dry season, where the mango and tamarind trees also thrive. The traditional cashew tree is tall (up to 14 m) and takes three years from planting before it starts production, and eight years before economic harvests can begin. More recent breeds, such as the dwarf cashew trees, are up to 6 m tall, and start producing after the first year, with economic yields after three years. The cashew nut yields for the traditional tree are about 0.25 metric tons per hectare, in contrast to over a ton per hectare for the dwarf variety. Grafting and other modern tree management technologies are used to further improve and sustain cashew nut yields in commercial orchards.


Production

In 2020, global production of cashew nuts (as the kernel) was 4,180,990 tonnes, led by Ivory Coast and India with a combined 39% of the world total (table). Vietnam, Burundi, and the Philippines also had significant production. Vietnam was the largest processor of cashew globally in 2020.


Trade

The top ten exporters of cashew nuts (in-shell; HS Code 080131) in value (USD) in 2021 were Ghana, Tanzania, Guinea-Bissau, Nigeria, Ivory Coast, Burkina Faso, Senegal, Indonesia, United Arab Emirates (UAE), and Guinea. From 2017 to 2021, the top ten exporters of cashew nuts (shelled; HS Code 080132) were Vietnam, India, the Netherlands, Germany, Brazil, Ivory Coast, Nigeria, Indonesia, Burkina Faso, and the United States.


Toxicity

Some people are allergic to cashews, but they are a less frequent allergen than tree nuts or peanuts. For up to 6% of children and 3% of adults, consuming cashews may cause allergic reactions, ranging from mild discomfort to life-threatening anaphylaxis. These allergies are triggered by the proteins found in tree nuts, and cooking often does not remove or change these proteins. Reactions to cashew and tree nuts can also occur as a consequence of hidden nut ingredients or traces of nuts that may inadvertently be introduced during food processing, handling, or manufacturing. The shell of the cashew nut contains oil compounds that can cause contact dermatitis similar to poison ivy, primarily resulting from the phenolic lipids,
anacardic acid Anacardic acids are phenolic lipids, chemical compounds found in the shell of the cashew nut (''Anacardium occidentale''). An acid form of urushiol, they also cause an allergic skin rash on contact, known as urushiol-induced contact dermatitis. An ...
, and cardanol. Due to the possible dermatitis, cashews are typically not sold in the shell to consumers. Readily and inexpensively extracted from the waste shells, cardanol is under research for its potential applications in nanomaterials and biotechnology.


Uses


Nutrition

Raw cashews are 5% water, 30%  carbohydrates, 44%  fat, and 18%  protein (table). In a 100-gram reference amount, raw cashews provide 553 
kilocalories The calorie is a unit of energy. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie was originally defined as the amount of heat needed to raise the temperature of on ...
, 67% of the Daily Value (DV) in total fats, 36% DV of protein, 13% DV of
dietary fiber Dietary fiber (in British English fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by the ...
and 11% DV of carbohydrates. Cashews are rich sources (20% or more of the DV) of dietary minerals, including particularly copper, manganese, phosphorus, and magnesium (79–110% DV), and of thiamin, vitamin B6 and vitamin K (32–37% DV). Iron, potassium, zinc, and selenium are present in significant content (14–61% DV) (table). Cashews (100 g, raw) contain of beta-sitosterol.


Nut and shell

Culinary uses for cashew seeds in snacking and cooking are similar to those for all tree seeds called nuts. Cashews are commonly used in South Asian cuisine, whole for garnishing sweets or curries, or ground into a paste that forms a base of sauces for curries (e.g., '' korma''), or some sweets (e.g., ''
kaju barfi Kaju katli (literally "cashew slice"), also known as kaju barfi, is an Indian dessert similar to a barfi. ''Kaju'' means cashew The cashew tree (''Anacardium occidentale'') is a tropical evergreen tree native to South America in the genus ...
''). It is also used in powdered form in the preparation of several Indian sweets and desserts. In Goan cuisine, both roasted and raw kernels are used whole for making curries and sweets. Cashews are also used in
Thai Thai or THAI may refer to: * Of or from Thailand, a country in Southeast Asia ** Thai people, the dominant ethnic group of Thailand ** Thai language, a Tai-Kadai language spoken mainly in and around Thailand *** Thai script *** Thai (Unicode block ...
and Chinese cuisines, generally in whole form. In the Philippines, cashew is a known product of Antipolo, and is eaten with ''suman''. The province of Pampanga also has a sweet dessert called ''turrones de casuy'', which is cashew
marzipan Marzipan is a confectionery, confection consisting primarily of sugar, honey, and almond meal (ground almonds), sometimes augmented with almond oil or extract. It is often made into Confectionery, sweets; common uses are chocolate-covered marzi ...
wrapped in white wafers. In Indonesia, roasted and salted cashews are called ''kacang mete'' or ''kacang mede'', while the cashew apple is called ''jambu monyet'' ( ‘monkey rose apple’). In the 21st century, cashew cultivation increased in several African countries to meet the demands for manufacturing
cashew milk Plant milk is a plant beverage with a color resembling that of milk. Plant milks are non-dairy beverages made from a water-based plant extract for flavoring and aroma. Plant milks are consumed as alternatives to milk, and often provide a crea ...
, a
plant milk Plant milk is a plant beverage with a color resembling that of milk. Plant milks are non-dairy beverages made from a water-based plant extract for flavoring and aroma. Plant milks are consumed as alternatives to milk, and often provide a crea ...
alternative to
dairy milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulating ...
. In Mozambique, ''bolo polana'' is a cake prepared using powdered cashews and mashed potatoes as the main ingredients. This dessert is popular in South Africa.


Apple

The mature cashew apple can be eaten fresh, cooked in curries, or fermented into vinegar, citric acid or an alcoholic drink. It is also used to make preserves, chutneys and jams in some countries such as India and Brazil. In many countries, particularly within South America, the cashew apple is used to flavor drinks, both alcoholic and nonalcoholic. In Brazil, cashew fruit juice and the fruit pulp are used in the production of sweets, juice, mixed with alcoholic beverages such as '' cachaça'', and as a flour, milk, or cheese. In Panama, the cashew fruit is cooked with water and sugar for a prolonged time to make a sweet, brown, paste-like dessert called ( being a Spanish name for cashew). Cashew nuts are more widely traded than cashew apples, because the fruit, unlike the nut, is easily bruised and has a very limited shelf life. Cashew apple juice, however, may be used for manufacturing blended juices. When consumed, the apple's
astringency An astringent (sometimes called adstringent) is a chemical that shrinks or constricts body tissues. The word derives from the Latin ''adstringere'', which means "to bind fast". Calamine lotion, witch hazel, and yerba mansa, a Californian plant ...
is sometimes removed by steaming the fruit for five minutes before washing it in cold water. Steeping the fruit in boiling salt water for five minutes also reduces the astringency. In Cambodia, where the plant is usually grown as an ornamental rather than an economic tree, the fruit is a delicacy and is eaten with salt.


Alcohol

In the Indian state of Goa, the ripened cashew apples are mashed and the juice is extracted and kept for fermentation for a few days which is called ''Neero''. Fermented juice then undergoes a double distillation process. The resulting beverage is called ''feni'' or fenny. ''Feni'' is about 40–42% alcohol (80–84 proof). The single-distilled version is called '' urrak'', which is about 15% alcohol (30 proof). In Tanzania, the cashew apple (''bibo'' in
Swahili Swahili may refer to: * Swahili language, a Bantu language official in Kenya, Tanzania and Uganda and widely spoken in the African Great Lakes * Swahili people, an ethnic group in East Africa * Swahili culture Swahili culture is the culture of ...
) is dried and reconstituted with water and fermented, then distilled to make a strong liquor called ''gongo''.


Nut oil

Cashew nut oil is a dark yellow oil derived from pressing the cashew nuts (typically from lower value broken chunks created accidentally during processing), and is used for cooking or as a salad dressing. The highest quality oil is produced from a single cold pressing.


Shell oil

Cashew nutshell liquid (CNSL) or cashew shell oil (
CAS registry number A CAS Registry Number (also referred to as CAS RN or informally CAS Number) is a unique identification number assigned by the Chemical Abstracts Service (CAS), US to every chemical substance described in the open scientific literature. It inclu ...
8007-24-7) is a natural resin with a yellowish sheen found in the honeycomb structure of the cashew nutshell, and is a byproduct of processing cashew nuts. It should not be confused with the edible cashew nut oil, as it is a strong irritant. It is therefore a danger in small-scale processing of the shells, but is a raw material having multiple possible uses. It is used in tropical folk medicine and for anti- termite treatment of timber. Its composition varies depending on how it is processed. * Cold, solvent-extracted CNSL is mostly composed of
anacardic acids Anacardic acids are phenolic lipids, chemical compounds found in the shell of the cashew nut (''Anacardium occidentale''). An acid form of urushiol, they also cause an allergic skin rash on contact, known as urushiol-induced contact dermatitis. An ...
(70%),
cardol Adipostatin A is an alkylresorcinol, a type of phenolic lipids composed of long aliphatic chains and phenolic rings. Chemically, it is similar in structure to urushiol, the irritant found in poison ivy. Adipostatin A can be found in ''Gingko ...
(18%) and cardanol (5%). * Heating CNSL decarboxylates the anacardic acids, producing a technical grade of CNSL that is rich in cardanol. Distillation of this material gives distilled, technical CNSL containing 78% cardanol and 8% cardol (cardol has one more hydroxyl group than cardanol). This process also reduces the degree of thermal polymerization of the unsaturated alkyl-phenols present in CNSL. * Anacardic acid is also used in the chemical industry for the production of cardanol, which is used for resins, coatings, and frictional materials. These substances are skin allergens, like
lacquer Lacquer is a type of hard and usually shiny coating or finish applied to materials such as wood or metal. It is most often made from resin extracted from trees and waxes and has been in use since antiquity. Asian lacquerware, which may be ca ...
and the oils of poison ivy, and they present a danger during manual cashew processing."World Agriculture and the Environment", by Jason W. Clay
p. 268
/ref> This natural oil phenol has interesting chemical structural features that can be modified to create a wide spectrum of biobased monomers. These capitalize on the chemically versatile construct, which contains three functional groups: the aromatic ring, the
hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy g ...
, and the double bonds in the flanking alkyl chain. These include polyols, which have recently seen increased demand for their biobased origin and key chemical attributes such as high reactivity, range of functionalities, reduction in blowing agents, and naturally occurring fire retardant properties in the field of rigid polyurethanes, aided by their inherent phenolic structure and larger number of reactive units per unit mass. CNSL may be used as a resin for carbon composite products. CNSL-based Novolac is another versatile industrial monomer deriving from cardanol typically used as a reticulating agent for
epoxy Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...
matrices in composite applications providing good thermal and mechanical properties to the final composite material.


Animal feed

Discarded cashew nuts unfit for human consumption, alongside the residues of oil extraction from cashew kernels, can be used to feed livestock. Animals can also eat the leaves of cashew trees.Heuzé V., Tran G., Hassoun P., Bastianelli D., Lebas F., 2017. Cashew (Anacardium occidentale) nuts and by-products. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://www.feedipedia.org/node/56


Other uses

As well as the nut and fruit, the plant has several other uses. In Cambodia, the bark gives a yellow dye, the timber is used in boat-making, and for house-boards, and the wood makes excellent charcoal. The shells yield a black oil used as a preservative and water-proofing agent in
varnish Varnish is a clear transparent hard protective coating or film. It is not a stain. It usually has a yellowish shade from the manufacturing process and materials used, but it may also be pigmented as desired, and is sold commercially in various ...
es, cements, and as a
lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
or timber seal. Timber is used to manufacture furniture, boats, packing crates, and
charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...
. Its juice turns black on exposure to air, providing an indelible ink.


See also

*
List of culinary nuts A culinary nut is a dry, edible fruit or seed that usually, but not always, has a high fat content. Nuts are used in a wide variety of edible roles, including in baking, as snacks (either roasted or raw), and as flavoring. In addition to bot ...
* '' Semecarpus anacardium'' (the Oriental Anacardium), a native of India and closely related to the cashew


References

{{Authority control Anacardium Crops originating from South America Edible nuts and seeds Medicinal plants of South America Nut oils Plants described in 1753 Resins Flora of South America Tropical agriculture Drupes Fruit trees