Thealmond (Prunus amygdalus,syn.Prunus dulcis (Mill.)D.A.Webb,nom. illeg. nonPrunus dulcis Rouchy) is a species of tree from the genusPrunus. Along with thepeach, it is classified in the subgenusAmygdalus, distinguished from the other subgenera by corrugations on the shell (endocarp) surrounding the seed.
The fruit of the almond is adrupe, consisting of an outer hull and ahard shell with the seed, which is not atrue nut.[3]Shelling almonds refers to removing the shell to reveal the seed. Almonds are sold shelled or unshelled.Blanched almonds are shelled almonds that have been treated with hot water to soften theseedcoat, which is then removed to reveal the whiteembryo. Once almonds are cleaned and processed, they can be stored for around a year if kept refrigerated; at higher temperatures they will becomerancid more quickly.[4] Almonds are used in many cuisines, often featuring prominently in desserts, such asmarzipan.[3]
The almond tree prospers in a moderateMediterranean climate with cool winter weather.[3] It is rarely found wild in its original setting.[5] Almonds were one of the earliest domesticatedfruit trees, due to the ability to produce quality offspring entirely from seed, without using suckers and cuttings. Evidence of domesticated almonds in theEarly Bronze Age has been found in the archeological sites of the Middle East, and subsequently across the Mediterranean region and similar arid climates with cool winters.
California produces about 80% of the world's almond supply.[3] Due to high acreage and water demand for almond cultivation, and need forpesticides,California almond production may be unsustainable, especially during the persistent drought and heat fromclimate change in the 21st century.[6]Droughts in California have caused some producers to leave the industry, leading to lower supply and increased prices.[6]
Description
The almond is adeciduous tree growing to 3–4.5 metres (10–15 feet) in height,[3][7] with a trunk of up to 30 centimetres (12 inches) in diameter. The youngtwigs are green at first, becoming purplish where exposed to sunlight, then grey in their second year. Theleaves are 8–13 cm (3–5 in) long,[8] with a serrated margin and a 2.5 cm (1 in)petiole.
The fragrantflowers are white to pale pink, 3–5 cm (1–2 in) diameter with five petals, produced singly or in pairs and appearing before the leaves in early spring.[3][9][10] Almond trees thrive in Mediterranean climates with warm, dry summers and mild, wet winters.[3] The optimal temperature for their growth is between 15 and 30 °C (59 and 86 °F) and the tree buds have achilling requirement of 200 to 700 hours below 7.2 °C (45.0 °F) to break dormancy.[11]
Almonds begin bearing an economic crop in the third year after planting. Trees reach full bearing five to six years after planting. The fruit matures in the autumn, 7–8 months after flowering.[10][12]
The almond fruit is 3.5–6 cm (1+3⁄8–2+3⁄8 in) long. It is not anut but adrupe. The outer covering, consisting of an outerexocarp, or skin, andmesocarp, or flesh, fleshy in other members ofPrunus such as theplum andcherry, is instead a thick, leathery, grey-green coat (with a downy exterior), called the hull. Inside the hull is a woodyendocarp which forms a reticulated, hard shell (like the outside of a peach pit) called thepyrena. Inside the shell is the edible seed, commonly called a nut.[3] Generally, one seed is present, but occasionally two occur. After the fruit matures, the hull splits and separates from the shell, and anabscission layer forms between the stem and the fruit so that the fruit can fall from the tree.[13] During harvest, mechanised tree shakers are used to expedite fruits falling to the ground for collection.[3]
The almond was namedAmygdalus communis byCarl Linnaeus in hisSpecies plantarum in 1753.[14] For the name 'Amygdalus' he referred toGaspard Bauhin'sPinax (1623). In 1801 the species was for the first time placed in the genusPrunus byAugust Batsch.[15] In that genus, the namePrunus communis was no longer available because in 1778William Hudson had already assigned it to a taxon in which he also included theplum (Prunus domestica).[16] Batsch thereupon named the speciesPrunus amygdalus, where 'amygdalus' is the old generic name and should therefore be treated as a noun in apposition. Meanwhile, in 1768,Philip Miller had published the name of what he believed to be a second species of almond:Amygdalus dulcis.[17] He mentioned Linnaeus'Amygdalus communis as the first species. It was not until 1967 that the combinationPrunus dulcis was published for the almond byDavid Allardice Webb, on the assumption thatAmygdalus dulcis was nothing more than a synonym ofAmygdalus communis, and thus an available name for that species. The epithetdulcis (1768) is older thanamygdalus (1801) and would therefore have priority. Webb noted that it was unfortunate that a species known for 165 years asPrunus amygdalus now had to be renamed under the rules of nomenclature. However, it later turned out that in 1967 the namePrunus dulcis was no longer available for the almond because it had already been used for a cherry in an 1878 publication by L'Abbé Rouchy.[18] The oldest valid combination inPrunus is thereforePrunus amygdalus.[19]
Sweet and bitter almonds
Almond blossomBlossoming of bitter almond tree
The seeds ofPrunus amygdalus var.dulcis are predominantly sweet[20][21] but some individual trees produce seeds that are somewhat more bitter.[3] The genetic basis for bitterness involves a single gene, the bitter flavour furthermore beingrecessive,[22][23] both aspects making this trait easier to domesticate. The fruits fromPrunus amygdalus var.amara are always bitter, as are the kernels from other species of genusPrunus, such as apricot, peach and cherry (although to a lesser extent).
The bitter almond is slightly broader and shorter than the sweet almond and contains about 50% of the fixed oil that occurs in sweet almonds. It also contains the enzymeemulsin which, in the presence of water, acts on the twosolubleglucosidesamygdalin andprunasin[24] yieldingglucose,cyanide and theessential oil of bitter almonds, which is nearly purebenzaldehyde, the chemical causing the bitter flavour. Bitter almonds may yield 4–9 milligrams ofhydrogen cyanide per almond[25] and contain 42 times higher amounts of cyanide than the trace levels found in sweet almonds.[26] The origin of cyanide content in bitter almonds is via theenzymatic hydrolysis of amygdalin.[26]P450monooxygenases are involved in the amygdalin biosynthetic pathway. A point mutation in abHLHtranscription factor preventstranscription of the two cytochrome P450 genes, resulting in the sweet kernel trait.[27]
The adjectiveamygdaloid (literally 'like an almond, almond-like') is used to describe objects which are roughly almond-shaped, particularly a shape which is part way between atriangle and anellipse. For example, the amygdala of the brain uses a direct borrowing of the Greek termamygdalē.[31]
The wild form of domesticated almond also grew in parts of the Levant.[33][36][37] Almond cultivation was spread by humans centuries ago along the shores of theMediterranean Sea into northern Africa and southern Europe,[33][34] and more recently to other world regions, notablyCalifornia.[3][38]
Selection of the sweet type from the many bitter types in the wild marked the beginning of almond domestication.[5][39] The wild ancestor of the almond used tobreed the domesticated species is unknown.[5][39] The speciesPrunus fenzliana may be the most likely wild ancestor of the almond, in part because it is native toArmenia andwestern Azerbaijan, where it was apparently domesticated.[5][33] Wild almond species were grown by early farmers, "at first unintentionally in the garbage heaps, and later intentionally in their orchards".[40]
Almonds were one of the earliest domesticatedfruit trees owing to their ability to be grown from seed,[5] allowing their cultivation to have perhaps predated the advent ofgrafting.[37]
Of the European countries that theRoyal Botanic Garden Edinburgh reported as cultivating almonds, Germany[43] is the northernmost, though the domesticated form can be found as far north as Iceland.[44]
Varieties
Almond trees are small to medium-sized but commercial cultivars can be grafted onto a different root-stock to produce smaller trees. Varieties include:
Nonpareil – originates in the 1800s. A large tree that produces large, smooth, thin-shelled almonds with 60–65% edible kernel per nut. Requires pollination from other almond varieties for good nut production.[45]
Tuono – originates in Italy. Has thicker, hairier shells with only 32% of edible kernel per nut. The thicker shell gives some protection from pests such as thenavel orangeworm. Does not require pollination by other almond varieties.[45]
Mariana – used as a rootstock to result in smaller trees
The most widely planted varieties of almond areself-incompatible; hence these trees require pollen from a tree with different genetic characters to produce seeds. Almond orchards therefore must grow mixtures of almond varieties. In addition, the pollen is transferred from flower to flower by insects; therefore commercial growers must ensure there are enough insects to perform this task.[47] The large scale of almond production in the U.S. creates a significant problem of providing enough pollinating insects. Additional pollinating insects are therefore brought to the trees. Thepollination ofCalifornia's almonds is the largest annualmanaged pollination event in the world, with over 1 million hives (nearly half of allbeehives in the U.S.) being brought to the almond orchards each February.[3][48]
Much of the supply of bees is managed by pollination brokers, who contract with migratorybeekeepers from at least 49 states for the event. This business was heavily affected bycolony collapse disorder at the turn of the 21st century, causing a nationwide shortage of honey bees and increasingthe price ofinsect pollination. To partially protect almond growers from these costs, researchers at theAgricultural Research Service, part of theUnited States Department of Agriculture (USDA), developedself-pollinating almond trees that combine this character with quality characters such as a flavour and yield.[45] Self-pollinating almond varieties exist, but they lack some commercial characters. However, through natural hybridisation between different almond varieties, a new variety that was self-pollinating with a high yield of commercial quality nuts was produced.
Almond production in California is concentrated mainly in theCentral Valley,[51] where the mild climate, rich soil, abundant sunshine and water supply make for ideal growing conditions. Due to thepersistent droughts in California in the early 21st century, it became more difficult to raise almonds in a sustainable manner.[52][48] The issue is complex because of the high amount of water needed to produce almonds: a single almond requires roughly 1.1 US gallons (0.92 imperial gallons; 4.2 litres) of water to grow properly.[51][52][53] Regulations related to water supplies are changing so some growers have destroyed their current almond orchards to replace with either younger trees or a different crop such aspistachio that needs less water.[54]
Almond tree with blossoming flowers,Valley of Elah, Israel
In 2023, world production of almonds was 3.5 milliontonnes, led by the United States with 51% of the total, followed by Spain and Australia as secondary producers (table).
United States
In the U.S., production is concentrated in California where 400,000 ha (1,000,000 acres) and six different almond varieties were under cultivation in 2017, with a yield of 2.25 billion pounds (1.02 billion kilograms) of shelled almonds.[58] California production is marked by a period of intense pollination during late winter byrented commercial bees transported by truck across the U.S. to almond groves, requiring more than half of the total U.S. commercial honeybee population.[59] The value of total U.S. exports of shelled almonds in 2016 was $3.2 billion.[60]
All commercially grown almonds sold as food in the U.S. are sweet cultivars. The U.S.Food and Drug Administration reported in 2010 that some fractions of imported sweet almonds were contaminated with bitter almonds, which contain cyanide.[61]
Spain has diverse commercial cultivars of almonds grown inCatalonia,Valencia,Murcia,Andalusia, andAragón regions, and theBalearic Islands.[64] The almond cultivar 'Marcona' is unique, having a kernel that is short, round, relatively sweet, and delicate in texture; it is marketed by name.[65] Its origin is unknown, but has been grown in Spain over centuries.[65]
Toxicity
Bitter almonds contain some 40 times the trace levels of cyanide found in sweet almonds.[26] Extract of bitter almond was once used medicinally, but even in small doses, its effects are severe or lethal, especially in children; the cyanide must be removed before consumption.[26] The acute oral lethal dose of cyanide for adult humans is reported to be 0.5–3.5 mg/kg (0.2–1.6 mg/lb) of body weight (approximately 50 bitter almonds), so that for children consuming 5–10 bitter almonds may be fatal.[26] Symptoms of eating such almonds includevertigo and other typical cyanide poisoning effects.[61]
Almonds are susceptible toaflatoxin-producing moulds.[67] Aflatoxins are potentcarcinogenic chemicals produced by moulds such asAspergillus flavus andAspergillus parasiticus.[68] The mould contamination may occur from soil, previously infested almonds, and almond pests such as navel-orange worm. High levels of mould growth typically appear as grey to black filament-like growth. It is unsafe to eat mould-infected tree nuts.
Some countries have strict limits on allowable levels of aflatoxin contamination of almonds and require adequate testing before the nuts can be marketed to their citizens. The European Union, for example, introduced a requirement since 2007 that all almond shipments to the EU be tested for aflatoxin. If aflatoxin does not meet the strict safety regulations, either the entire consignment must be reprocessed to eliminate the aflatoxin or it must be destroyed.[69][70]
Breeding programs have found a trait known ashigh shell-seal.[46] High shell-seal providesresistance against theseAspergillus species and so against the development of their toxins.[46]
Mandatory pasteurization in California
After tracing cases ofsalmonellosis to almonds, the USDA approved a proposal by the Almond Board of California to pasteurize almonds sold to the public. After publishing the rule in March 2007, the almond pasteurization program became mandatory for California companies effective 1 September 2007.[71] Raw, untreated California almonds have not been commercially available in the U.S. since then.
California almonds labeled "raw" must be steam-pasteurized or chemically treated withpropylene oxide (PPO). This does not apply to imported almonds[72] or almonds sold from the grower directly to the consumer in small quantities.[73] The treatment also is not required for raw almonds sold for export outside of North America.
The Almond Board of California states: "PPO residue dissipates after treatment". TheU.S. Environmental Protection Agency has reported: "Propylene oxide has been detected in fumigated food products; consumption of contaminated food is another possible route of exposure". PPO is classified asGroup 2B ("possibly carcinogenic to humans").[74]
The USDA-approved marketing order was challenged in court by organic farmers organized by theCornucopia Institute, a Wisconsin-based farm policy research group which filed a lawsuit in September 2008. According to the institute, this almond marketing order has imposed significant financial burdens on small-scale and organic growers and damaged domestic almond markets. A federal judge dismissed the lawsuit in early 2009 on procedural grounds. In August 2010, a federal appeals court ruled that the farmers have a right to appeal the USDA regulation. In March 2013, the court vacated the suit on the basis that the objections should have been raised in 2007 when the regulation was first proposed.[75]
Almonds are included as a good source of protein among recommended healthy foods by the USDA.[79] A 2016 review ofclinical research indicated that regular consumption of almonds may reduce the risk ofheart disease by lowering blood levels ofLDL cholesterol.[80][81]
While the almond is often eaten on its own, raw or toasted, it is also a component of various dishes. Almonds are available in many forms, such as whole, slivered, and ground into flour. Almond pieces around2–3 millimetres (1⁄16–1⁄8 in) in size, called "nibs", are used for special purposes such as decoration.[82]
A wide range of classic sweets feature almonds as a central ingredient. Marzipan was developed in the Middle Ages. Since the 19th century almonds have been used to make bread,almond butter, cakes and puddings, candied confections, almond cream-filled pastries,nougat, cookies (macaroons,biscotti andqurabiya), and cakes (financiers,Esterházy torte), and other sweets and desserts.[83]
The young, developing fruit of the almond tree can be eaten whole (green almonds) when they are still green and fleshy on the outside and the inner shell has not yet hardened. The fruit is somewhat sour, but is a popular snack in parts of the Middle East, eaten dipped in salt to balance the sour taste. Also in the Middle East they are often eaten with dates. They are available only from mid-April to mid-June in the Northern Hemisphere; pickling or brining extends the fruit's shelf life.
InFrench cuisine, alternating layers of almond and hazelnutmeringue are used to make the dessertdacquoise.Pithivier is one of many almond cream-filled pastries.
InGermany, Easter bread calledDeutsches Osterbrot is baked with raisins and almonds.
In Greece almond flour is used to makeamygdalopita, aglyka tapsiou dessert cake baking in a tray. Almonds are used forkourabiedes, a Greek version of the traditionalquarabiya almond biscuits. A soft drink known assoumada is made from almonds in various regions.
In Iran, green almonds are dipped insea salt and eaten as snacks on street markets; they are calledchaqale bâdam. Candied almonds callednoghl are served alongside tea and coffee. Also, sweet almonds are used to prepare special food for babies, namedharire badam. Almonds are added to some foods, cookies, and desserts, or are used to decorate foods. People in Iran consume roasted nuts for special events, for example, during New Year (Nowruz) parties.
In Italy,colomba di Pasqua is a traditionalEaster cake made withalmonds. Bitter almonds are the base foramaretti cookies, a common dessert. Almonds are also a common choice as the nuts to include intorrone.
In Morocco, almonds in the form of sweet almond paste are the main ingredient in pastry fillings and severalother desserts. Fried blanched whole almonds are also used to decorate sweettajines such as lamb with prunes. Southwestern Berber regions ofEssaouira and Souss are also known foramlou, a spread made of almond paste,argan oil, and honey. Almond paste is also mixed with toasted flour and among others, honey, olive oil or butter, anise, fennel, sesame seeds, and cinnamon to makesellou (also calledzamita inMeknes orslilou inMarrakesh), a sweet snack known for its long shelf life and high nutritive value.
InIndian cuisine, almonds are the base ingredients ofpasanda-style andMughlaicurries.Badam halva is a sweet made from almonds with added colouring. Almond flakes are added to many sweets (such assohan barfi), and are usually visible sticking to the outer surface. Almonds form the base of various drinks which are supposed to have cooling properties. Almondsherbet orsherbet-e-badaam, is a common summer drink. Almonds are also sold as a snack with added salt.
In Israel almonds are used as a topping fortahini cookies or eaten as a snack.
In SpainMarcona almonds are usually toasted in oil and lightly salted. They are used by Spanish confectioners to prepare a sweet calledturrón.
Almonds can be processed into amilk substitute called almond milk; the nut's soft texture, mild flavour, and light colouring (when skinned) make for an efficient analog to dairy, and a soy-free choice forlactose intolerant people andvegans. Raw, blanched, and lightly toasted almonds work well for different production techniques, some of which are similar to that ofsoy milk and some of which use no heat, resulting inraw milk.
Almond milk, along with almond butter and almond oil, are versatile products used in both sweet and savoury dishes.
InMoroccan cuisine, sharbat billooz, a common beverage, is made by blending blanched almonds with milk, sugar and other flavourings.[86]
Flour and skins
Almond flour or groundalmond meal combined with sugar or honey as marzipan is often used as agluten-free alternative to wheat flour in cooking and baking.[87]
Due to the cyanide found in bitter almonds, modern syrups generally are produced only from sweet almonds. Such syrup products do not contain significant levels ofhydrocyanic acid, so are generally considered safe for human consumption.[26]
When almond oil is analyzed separately and expressed per 100 grams as a reference mass, the oil provides 3,700 kJ (884 kcal) of food energy, 8 grams of saturated fat (81% of which is palmitic acid), 70 grams of oleic acid, and 17 grams of linoleic acid (oil table).
Oleum amygdalae, the fixed oil, is prepared from either sweet or bitter almonds, and is a glyceryl oleate with a slight odour and a nutty taste. It is almost insoluble inalcohol but readily soluble inchloroform orether. Almond oil is obtained from the driedkernel of almonds.[93] Sweet almond oil is used as a carrier oil in aromatherapy and cosmetics while bitter almond oil, containing benzaldehyde, is used as a food flavouring and in perfume.[47]
The almond is highly revered in some cultures. The tree originated in the Middle East. In the Bible, the almond is mentioned ten times, beginning withGenesis 43:11,[95] where it is described as "among the best of fruits". InNumbers 17,Levi is chosen from the other tribes of Israel byAaron's rod, which brought forth almond flowers.[95] The almond blossom supplied a model for themenorah which stood in theHoly Temple,[95] "Three cups, shaped like almond blossoms, were on one branch, with a knob and a flower; and three cups, shaped like almond blossoms, were on the other … on the candlestick itself were four cups, shaped like almond blossoms, with its knobs and flowers" (Exodus 25:33–34; 37:19–20). InJeremiah 1:11–12, the vision of an almond branch conveys a wordplay in Hebrew betweenshaqed (almond) andshoqed (watching), symbolizing God's vigilant commitment to fulfill His word.[95] ManySephardic Jews give five almonds to each guest before special occasions like weddings.[96]
Similarly,Christian symbolism often uses almond branches as a symbol of thevirgin birth of Jesus; paintings andicons often includealmond-shaped haloes encircling theChrist Child and as a symbol ofMary. The word "luz", which appears in Genesis 30:37, sometimes translated as "hazel", may actually be derived from theAramaic name for almond (Luz), and is translated as such in theNew International Version and other versions of the Bible.[97] The Arabic name for almond is لوز "lauz" or "lūz". In some parts of the Levant and North Africa, it is pronounced "loz", which is very close to its Aramaic origin.
TheEntrance of the flower (La entrada de la flor) is an event celebrated on 1 February inTorrent, Spain, in which the clavarios and members of the Confrerie of the Mother of God deliver a branch of the first-blooming almond-tree to the Virgin.[98]
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