Almond

The almond (Prunus amygdalus, syn. Prunus dulcis) is a species of tree native to Iran and surrounding countries[4] and ancient remains of almonds were discovered in the Levant area.[5] The almond is also the name of the edible and widely cultivated seed of this tree. Within the genus Prunus, it is classified with the peach in the subgenus Amygdalus, distinguished from the other subgenera by corrugations on the shell (endocarp) surrounding the seed.[citation needed ]

The fruit of the almond is a drupe, consisting of an outer hull and a hard shell with the seed, which is not a true nut, inside. 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 the seedcoat, which is then removed to reveal the white embryo.

The almond is a deciduous tree, growing 4–10 m (13–33 ft) in height, with a trunk of up to 30 cm (12 in) in diameter. The young twigs are green at first, becoming purplish where exposed to sunlight, then grey in their second year. The leaves are 8–13 cm (3–5 in) long,[6] with a serrated margin and a 2.5 cm (1 in) petiole. The flowers 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.[7][8] Almond grows best in Mediterranean climates with warm, dry summers and mild, wet winters. The optimal temperature for their growth is between 15 and 30 °C (59 and 86 °F) and the tree buds have a chilling requirement of 200 to 700 hours below 7.2 °C (45.0 °F) to break dormancy.[9]

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.[8][10]

The almond fruit is 3.5–6 cm (1+ 3 ⁄8 –2+ 3 ⁄8  in) long. In botanical terms, it is not a nut but a drupe. The outer covering or exocarp, fleshy in other members of Prunus such as the plum and cherry, is instead a thick, leathery, grey-green coat (with a downy exterior), called the hull. Inside the hull is a woody endocarp which forms a reticulated, hard shell (like the outside of a peach pit) called the pyrena. Inside the shell is the edible seed, commonly called a nut. Generally, one seed is present, but occasionally two occur. After the fruit matures, the hull splits and separates from the shell, and an abscission layer forms between the stem and the fruit so that the fruit can fall from the tree.[11]

Green almonds

Almond shell

Blanched almonds

Almond is native to Iran and surrounding countries[4] and ancient remains of almonds were discovered in the Levant area.[5] It was spread by humans in ancient times along the shores of the Mediterranean into northern Africa and southern Europe, and more recently transported to other parts of the world, notably California, United States.[13] The wild form of domesticated almond grows in parts of the Levant.[14]

Selection of the sweet type from the many bitter types in the wild marked the beginning of almond domestication. It is unclear as to which wild ancestor of the almond created the domesticated species. The species Prunus fenzliana may be the most likely wild ancestor of the almond, in part because it is native to Armenia and western Azerbaijan, where it was apparently domesticated.[5] Wild almond species were grown by early farmers, "at first unintentionally in the garbage heaps, and later intentionally in their orchards".[15]

Almonds were one of the earliest domesticated fruit trees, due to "the ability of the grower to raise attractive almonds from seed.[5] Thus, in spite of the fact that this plant does not lend itself to propagation from suckers or from cuttings, it could have been domesticated even before the introduction of grafting".[14] Domesticated almonds appear in the Early Bronze Age (3000–2000 BC), such as the archaeological sites of Numeira (Jordan),[5] or possibly earlier. Another well-known archaeological example of the almond is the fruit found in Tutankhamun's tomb in Egypt (c. 1325 BC), probably imported from the Levant.[14] An article on almond tree cultivation in Spain is brought down in Ibn al-'Awwam's 12th-century agricultural work, Book on Agriculture.[16]

Of the European countries that the Royal Botanic Garden Edinburgh reported as cultivating almonds, Germany[17] is the northernmost, though the domesticated form can be found as far north as Iceland.[18]

The word "almond" comes from Old French almande or alemande, Late Latin *amandula, *amindula, derived from amygdala from the Ancient Greek ἀμυγδάλη (amygdálē)[19] (cf. amygdala, an almond-shaped portion of the brain).[20] The al- in English, for the a- used in other languages may be due a confusion with the Arabic article al, the word having first dropped the a- as in the Italian form mandorla; the British pronunciation ah-mond and the modern Catalan ametlla and modern French amande show a form of the word closer to the original.

The adjective "amygdaloid" (literally "like an almond") is used to describe objects which are roughly almond-shaped, particularly a shape which is part way between a triangle and an ellipse. See, for example, the brain structure amygdala, which uses a direct borrowing of the Greek term amygdalē.[21]

Almond trees are small to medium sized but commercial cultivars can be grafted onto a different root-stock to produce smaller trees. Varieties include:

The most widely planted varieties of almond are self-incompatible that require pollination from a tree with different genetic characters in order to produce seeds. Almond orchards therefore need to grow mixtures of almond varieties. In addition, the pollen is transferred from flower to flower by insects, so that commercial growers have to ensure there are adequate insects to perform this task.[23] The large scale of almond production in the U.S. provides a significant problem. Additional pollinating insects are therefore brought to the trees. The pollination of California's almonds is the largest annual managed pollination event in the world, with 1.4 million hives (nearly half of all beehives in the US) being brought to the almond orchards each February.[24]

Much of the supply of bees is managed by pollination brokers, who contract with migratory beekeepers from at least 49 states for the event. This business was heavily affected by colony collapse disorder at the turn of the twenty-first century, causing a nationwide shortage of honey bees and increasing the price of insect pollination. To partially protect almond growers from these costs, researchers at the USA government Agricultural Research Service have developed self-pollinating almond trees that combine this character with quality characters such as a flavor and yield.[22] Self-pollinating almond varieties exist but lack some commercial characters. However, through natural hybridisation between different almond varieties, a new one that was self-pollinating with a high yield of commercial quality nuts was produced.

A grove of almond trees

Almond blossoms

Young almond fruit

Mature almond fruit

An almond shaker before and during a harvest of a tree

Almond trees can be attacked by an array of damaging organisms, including insects, fungal pathogens, plant viruses, and bacteria.[25]

Almond production in California is concentrated mainly in the Central Valley,[26] where the mild climate, rich soil, abundant sunshine and water supply make for ideal growing conditions. Due to the persistent droughts in California in the early 21st century, it became more difficult to raise almonds in a sustainable manner.[27][24] 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.[26][27][28] 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 as pistachio that needs less water.[29]

Sustainability strategies implemented by the Almond Board of California and almond farmers include:[24][30][31]

In 2019, world production of almonds was 3.5 million tonnes, led by the United States providing 55% of the world total (table). Other leading producers were Spain, Iran, and Turkey.

In the United States, production is concentrated in California where 1,000,000 acres (400,000 ha) and six different almond varieties were under cultivation in 2017, with a yield of 2.25 billion lb (1.02 billion kg) of shelled almonds.[33] California production is marked by a period of intense pollination during late winter by rented commercial bees transported by truck across the United States to almond groves, requiring more than half of the total US honeybee population.[34] The value of total US exports of shelled almonds in 2016 was $3.2 billion.[35]

Spain has diverse commercial cultivars of almonds grown in Catalonia, Valencia, Murcia, Andalusia, and Aragón regions, and the Balearic Islands.[36] Production in 2016 declined 2% nationally compared to 2015 production data.[36]

The 'Marcona' almond cultivar is recognizably different from other almonds and is marketed by name.[37] The kernel is short, round, relatively sweet, and delicate in texture. Its origin is unknown and has been grown in Spain for a long time; the tree is very productive, and the shell of the nut is very hard.[37]

Australia is the largest almond production region in the Southern Hemisphere. Most of the almond orchards are located along the Murray River corridor in New South Wales, Victoria, and South Australia.[38][39]

The seeds of Prunus dulcis var. dulcis are predominantly sweet[40][41] but some individual trees produce seeds that are somewhat more bitter. The genetic basis for bitterness involves a single gene, the bitter flavor furthermore being recessive,[42][43] both aspects making this trait easier to domesticate. The fruits from Prunus dulcis var. amara are always bitter, as are the kernels from other species of genus Prunus, 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 enzyme emulsin which, in the presence of water, acts on the two soluble glucosides amygdalin and prunasin[44] yielding glucose, cyanide and the essential oil of bitter almonds, which is nearly pure benzaldehyde, the chemical causing the bitter flavor. Bitter almonds may yield 4–9 mg of hydrogen cyanide per almond[45] and contain 42 times higher amounts of cyanide than the trace levels found in sweet almonds.[46] The origin of cyanide content in bitter almonds is via the enzymatic hydrolysis of amygdalin.[46] P450 monooxygenases are involved in the amygdalin biosynthetic pathway. A point mutation in a bHLH transcription factor prevents transcription of the two cytochrome P450 genes, resulting in the sweet kernel trait.[47]

Extract of bitter almond was once used medicinally but even in small doses, effects are severe or lethal, especially in children; the cyanide must be removed before consumption.[46] 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.[46]

All commercially grown almonds sold as food in the United States are sweet cultivars. The US Food and Drug Administration reported in 2010 that some fractions of imported sweet almonds were contaminated with bitter almonds. Eating such almonds could result in vertigo and other typical bitter almond (cyanide) poisoning effects.[48]

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 around 2–3 mm in size, called "nibs", are used for special purposes such as decoration.[49]

Almonds are a common addition to breakfast muesli or oatmeal.

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 and qurabiya), and cakes (financiers, Esterházy torte), and other sweets and desserts.[50]

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.

Certain natural food stores sell "bitter almonds" or "apricot kernels" labeled as such, requiring significant caution by consumers for how to prepare and eat these products.[53]

Marzipan, a smooth, sweetened almond paste, is used in a number of elegant cakes and desserts. Princess cake is covered by marzipan (similar to fondant), as is Battenberg cake. In Sicily, sponge cake is covered with marzipan to make cassatella di sant'Agata and cassata siciliana, and marzipan is dyed and crafted into realistic fruit shaped to make frutta martorana. The Andalusian Christmas pastry pan de Cádiz is filled with marzipan and candied fruit.

Almonds can be processed into a milk substitute called almond milk; the nut's soft texture, mild flavor, and light coloring (when skinned) make for an efficient analog to dairy, and a soy-free choice for lactose intolerant people and vegans. Raw, blanched, and lightly toasted almonds work well for different production techniques, some of which are similar to that of soymilk and some of which use no heat, resulting in "raw milk" (see raw foodism).

Almond milk, along with almond butter and almond oil, are a versatile products used in both sweet and savoury dishes.

In Moroccan cuisine, sharbat billooz is one of the best known beverages, served for weddings, it is made by blending blanched almonds with milk, sugar and other flavorings.[54]

Almond flour or ground almond meal combined with sugar or honey as marzipan is often used as a gluten-free alternative to wheat flour in cooking and baking.[55]

Almonds contain polyphenols in their skins consisting of flavonols, flavan-3-ols, hydroxybenzoic acids and flavanones[56] analogous to those of certain fruits and vegetables. These phenolic compounds and almond skin prebiotic dietary fiber have commercial interest as food additives or dietary supplements.[56][57]

Historically, almond syrup was an emulsion of sweet and bitter almonds, usually made with barley syrup (orgeat syrup) or in a syrup of orange flower water and sugar, often flavored with a synthetic aroma of almonds.[46] Orgeat syrup is an important ingredient in the Mai Tai and many other Tiki drinks.[58][59][60]

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 of hydrocyanic acid, so are generally considered safe for human consumption.[46]

Almonds are 4% water, 22% carbohydrates, 21% protein, and 50% fat (table). In a 100-gram (3+ 1 ⁄2 -ounce) reference amount, almonds supply 2,420 kilojoules (579 kilocalories) of food energy. The almond is a nutritionally dense food (table), providing a rich source (20% or more of the Daily Value, DV) of the B vitamins riboflavin and niacin, vitamin E, and the essential minerals calcium, copper, iron, magnesium, manganese, phosphorus, and zinc. Almonds are a moderate source (10–19% DV) of the B vitamins thiamine, vitamin B6, and folate, choline, and the essential mineral potassium. They also contain substantial dietary fiber, the monounsaturated fat, oleic acid, and the polyunsaturated fat, linoleic acid. Typical of nuts and seeds, almonds are a source of phytosterols such as beta-sitosterol, stigmasterol, campesterol, sitostanol, and campestanol.[61]

Almonds are included as a good source of protein among recommended healthy foods by the US Department of Agriculture.[62] A 2016 review of clinical research indicated that regular consumption of almonds may reduce the risk of heart disease by lowering blood levels of LDL cholesterol.[63][64]

Almonds may cause allergy or intolerance. Cross-reactivity is common with peach allergens (lipid transfer proteins) and tree nut allergens. Symptoms range from local signs and symptoms (e.g., oral allergy syndrome, contact urticaria) to systemic signs and symptoms including anaphylaxis (e.g., urticaria, angioedema, gastrointestinal and respiratory symptoms).[65]

Almonds are a rich source of oil, with 50% of kernel dry mass as fat (whole almond nutrition table). In relation to total dry mass of the kernel, almond oil contains 32% monounsaturated oleic acid (an omega-9 fatty acid), 13% linoleic acid (a polyunsaturated omega-6 essential fatty acid), and 10% saturated fatty acid (mainly as palmitic acid, USDA link in table). Linolenic acid, a polyunsaturated omega-3 fat, is not present (table). Almond oil is a rich source of vitamin E, providing 261% of the Daily Value per 100 ml (table).

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 in alcohol but readily soluble in chloroform or ether. Almond oil is obtained from the dried kernel of almonds.[66] 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.[23]

Almonds are susceptible to aflatoxin-producing molds.[67] Aflatoxins are potent carcinogenic chemicals produced by molds such as Aspergillus flavus and Aspergillus parasiticus.[68] The mold contamination may occur from soil, previously infested almonds, and almond pests such as navel-orange worm. High levels of mold growth typically appear as gray to black filament like growth. It is unsafe to eat mold-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 EU be tested for aflatoxin. If aflatoxin does not meet the strict safety regulations, the entire consignment may be reprocessed to eliminate the aflatoxin or it must be destroyed.[69][70]

The USDA approved a proposal by the Almond Board of California to pasteurize almonds sold to the public, after tracing cases of salmonellosis to almonds. The almond pasteurization program became mandatory for California companies in 2007.[71] Raw, untreated California almonds have not been available in the U.S. since then.

California almonds labeled "raw" must be steam-pasteurized or chemically treated with propylene 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". The U.S. EPA has reported: "Propylene oxide has been detected in fumigated food products; consumption of contaminated food is another possible route of exposure". PPO is classified as Group 2B ("possibly carcinogenic to humans").[74]

The USDA-approved marketing order was challenged in court by organic farmers organized by the Cornucopia Institute, a Wisconsin-based farm policy research group. According to the Cornucopia 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 the spring of 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]

The almond is highly revered in some cultures. The tree originated in the Middle East,[76] and is mentioned numerous times in the Bible.

In the Hebrew Bible, the almond was a symbol of watchfulness and promise due to its early flowering.[citation needed ] In the Bible the almond is mentioned ten times, beginning with Book of Genesis 43:11, where it is described as "among the best of fruits". In Numbers 17 Levi is chosen from the other tribes of Israel by Aaron's rod, which brought forth almond flowers. According to tradition, the rod of Aaron bore sweet almonds on one side and bitter on the other; if the Israelites followed the Lord, the sweet almonds would be ripe and edible, but if they were to forsake the path of the Lord, the bitter almonds would predominate.[citation needed ] The almond blossom supplied a model for the menorah which stood in the Holy Temple, "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). Many Sephardic Jews give 5 almonds to each guest before special occasions like weddings.[77]

Similarly, Christian symbolism often uses almond branches as a symbol of the Virgin Birth of Jesus; paintings and icons often include almond-shaped haloes encircling the Christ Child and as a symbol of Mary. The word "Luz", which appears in Genesis 30:37, sometimes translated as "hazel", may actually be derived from the Aramaic name for almond (Luz), and is translated as such in some Bible versions such as the NIV.[78] 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.

La entrada de la flor is an event celebrated on 1 February in Torrent, 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.[79]