Monday, January 2, 2012

Nut of the Week - Almonds

Almond tree with ripening fruit.
The almond (Prunus dulcis, syn. Prunus amygdalus Batsch., Amygdalus communis L., Amygdalus dulcis Mill.), is a species of tree native to the Middle East and South Asia. 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 the corrugated shell (endocarp) surrounding the seed.

The fruit of the almond is not a true nut, but a drupe, consisting of an outer hull and a hard shell with the seed ("nut") inside. Shelling almonds refers to removing the shell to reveal the seed. Almonds are commonly sold shelled (i.e., after the shells are removed), or unshelled (i.e., with the shells still attached). 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 small deciduous tree, growing 13–33 ft in height, with a trunk of up to 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 3–5 inches long, with a serrated margin and 1 in)petiole. The flowers are white or pale pink, 1–2 in diameter with five petals, produced singly or in pairs before the leaves in early spring.

Almonds begin bearing an economic crop in the third year after planting. Trees reach full bearing after five to six years after planting. The fruit is mature in the autumn, 7–8 months after flowering.

In botanical terms, the almond fruit is not a nut, but a drupe 1–2 in long. 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 reticulated hard woody shell (like the outside of a peach pit) called the endocarp. Inside the shell is the edible seed, commonly called a nut. Generally, one seed is present, but occasionally there are two.

The almond is a native to the Mediterranean climate region of the Middle East, eastward as far as the Indus. 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.

The wild form of domesticated almond grows in parts of the Levant; almonds must first have been taken into cultivation in this region. The fruit of the wild forms contains the glycoside amygdalin, "which becomes transformed into deadly prussic acid (hydrogen cyanide) after crushing, chewing, or any other injury to the seed."

However, domesticated almonds are not toxic; Jared Diamond argues that a common genetic mutation causes an absence of glycoside amygdalin, and this mutant was grown by early farmers, "at first unintentionally in the garbage heaps, and later intentionally in their orchards". Zohary and Hopf believe that almonds were one of the earliest domesticated fruit trees due to "the ability of the grower to raise attractive almonds from seed. 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". Domesticated almonds appear in the Early Bronze Age (3000–2000 BC) of the Near East, or possibly a little earlier. A 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. Of the European countries that the Royal Botanic Garden Edinburgh reported as cultivating almonds, Germany is the northernmost, though the domesticated form can be found as far north as Iceland.

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, sliced (flaked, slivered), and as almond butter, almond milk and almond oil. These variations can be used in both sweet and savory dishes.

Along with other nuts, sweet almonds can be sprinkled over desserts, particularly ice cream based dishes. Sweet almonds are used in marzipan, nougat, many pastries (including jesuites), cookies (including French macarons, macaroons), and cakes (including financiers), noghl and other sweets and desserts. They are also used to make almond butter, a spread similar to peanut butter, popular with peanut allergy sufferers and for its less salty taste. 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. Available only from mid April to mid June (northern hemisphere), pickling or brining extends the fruit's shelf life.

    In China, almonds are used in a popular dessert where they are mixed with milk and then served hot.

    In Greece, ground blanched almonds are used as the base material in a great variety of desserts, usually called amygdalota. Because of their white color, most are traditionally considered "wedding sweets" and are served at wedding banquets. In addition, a soft drink known as soumada is made from almonds in various regions.

    In Iran, green almonds are dipped in sea salt and eaten as snacks on street markets; they are called Chaqalu bâdom.

    In Italy, the bitter almonds from apricots are the base for amaretti (almond macaroons), a common dessert. Traditionally, a low percentage of bitter almonds (10-20%) is added to the ingredients, which gives the cookies their bitter taste (commercially, apricot kernels are used as a substitute for bitter almonds). Almonds are also a common choice as the nuts to include in torrone. In Puglia and Sicily, "pasta di mandorle" (almond paste) is used to make small soft cakes, often decorated with jam, pistacchio or chocolate.

    In Morocco, almonds in the form of sweet almond paste are the main ingredient in pastry fillings, and several other desserts. Fried blanched whole almonds are also used to decorate sweet tajines such as lamb with prunes. A drink made from almonds mixed with milk is served in important ceremonies such as weddings and can also be ordered in some cafes. Southwestern Berber regions of Essaouira and Souss are also known for "Amlou" 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 make "Sellou" (also called "Zamita" in Meknes or "Slilou" in Marrakech), a sweet snack known for its long shelf life and high nutritive value.

    In India, almonds are the base ingredients of pasanda-style curries. Badam halva is a sweet made from almonds with added coloring. Almond flakes are added to many sweets (such as sohan barfi), and are usually visible sticking to the outer surface.

    In Pakistan, almonds are the base ingredients of many food items. Meat dishes containing almonds include pasanda-style or Mughalai curries. Badam halva is a sweet made from almonds with added coloring. Almond flakes are added to many sweets (such as sohan barfi), and are usually visible sticking to the outer surface. Almonds form the base of various drinks which are supposed to have cooling properties. Almond sherbet or 'Sherbet-e-Badaam' in Urdu, is a popular summer drink. Almonds are also sold as a snack with added salt.

Almonds can be processed into a milk substitute called almond milk; the nut's soft texture, mild flavor, and light colouring (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".

The 'Marcona' almond cultivar is recognizably different from other almonds, and is marketed by name. The kernel is short, round, relatively sweet and delicate in texture. It has been grown in Spain for a long time and its origin is unknown; the tree is very productive, the shell of the nut very hard. 'Marcona' almonds are traditionally served after being lightly fried in oil, and are used by Spanish chefs to prepare a dessert called turrón.

The sweet almond contains about 26% carbohydrates (12% dietary fiber, 6.3% sugars, 0.7% starch and the rest miscellaneous carbohydrates), and may therefore be made into flour for cakes and cookies (biscuits) for low-carbohydrate diets. A standard serving of almond flour, 1 cup, contains 20 grams of carbohydrates, of which 10 g is dietary fiber, for a net of 10 g of carbohydrate per cup. This makes almond flour very desirable for use in cake and bread recipes by people on carbohydrate-restricted diets.

Almonds are a rich source of vitamin E, containing 26 mg per 100 g.  They are also rich in dietary fiber, B vitamins, essential minerals and monounsaturated fat (see nutrient table), one of the two "good" fats which potentially may lower LDL cholesterol. Typical of nuts and seeds, almonds also contain phytosterols, associated with cholesterol-lowering properties.

Potential health benefits, which have not been scientifically validated, include improved complexion and possibly a lower risk of cancer. Preliminary research associates consumption of almonds with elevating blood levels of high density lipoproteins and lowering low density lipoproteins. A preliminary trial showed that, in spite of the high fat content of almonds, using them in the daily diet might lower several factors associated with heart disease, including cholesterol and blood lipids.

Almonds contain polyphenols in their skins analogous to those of certain fruits and vegetables.

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

Unshelled (left) and shelled (right) almonds

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