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|Macadamia integrifolia nuts on the tree|
|Macadamia integrifolia nuts on the tree|
Macadamia is a genus of four species of trees indigenous to Australia and constituting part of the plant family Proteaceae. They grow naturally in north eastern New South Wales and central and south eastern Queensland. Common names include macadamia, macadamia nut, Queensland nut, bush nut, maroochi nut, queen of nuts and bauple nut; and from Indigenous Australians' languages bauple, gyndl, jindilli, and boombera. Previously, more species, with disjunct distributions, were named as members of this genus Macadamia. Genetics and morphological studies more recently published in 2008 by Austin Mast and colleagues, show they have separated from this genus Macadamia, correlating less closely than thought from earlier morphological studies. The species previously named in this Macadamia genus, may still be referred to overall by the descriptive, non-scientific name of macadamia; their disjunct distributions and current scientific names are:
Macadamia species grow as small to large evergreen trees 2–12 m (6.6–39.4 ft) tall. The leaves are arranged in whorls of three to six, lanceolate to obovate or elliptical in shape, 6–30 cm long and 2–13 cm broad, with an entire or spiny-serrated margin. The flowers are produced in a long, slender, simple raceme 5–30 cm long, the individual flowers 10–15 mm long, white to pink or purple, with four tepals. The fruit is a very hard, woody, globose follicle with a pointed apex, containing one or two seeds.
The seeds are a valuable food crop. Only three of the species, Macadamia integrifolia, Macadamia ternifolia, and Macadamia tetraphylla, are of commercial importance. Only 2 of these 3 species (Macadamia integrifolia and Macadamia tetraphylla) can be eaten raw. The remainder of the genus possesses poisonous and/or inedible seeds, such as M. whelanii and M. ternifolia; the toxicity is due to the presence of cyanogenic glycosides. These glycosides can be removed by prolonged leaching, a practice used by some Indigenous Australian peoples for these species, as well.
The two species of edible macadamia readily hybridize, and M. tetraphylla is threatened in the wild due to this. The seed was first described by Europeans south of Brisbane in 1828 by the explorer and botanist Allan Cunningham. One of the locations where wild macadamia trees were originally found was at Mount Bauple near Maryborough in southeast Queensland, Australia. Macadamia nuts are one of the few Australian endemic plant foods produced and exported in the quantities of a commodity.
The first commercial orchard of macadamia trees was planted in the early 1880s by Rous Mill, 12 kilometres (7.5 mi) southeast of Lismore, New South Wales, consisting of M. tetraphylla. Besides the development of a small boutique industry in Australia during the late 19th and early 20th centuries, macadamia was extensively planted as a commercial crop in Hawaii from the 1920s. Macadamia seeds were first imported into Hawaii in 1882 by William H. Purvis. The young manager of the Pacific Sugar Mill at Kukuihaele on the Big Island, planted seeds that year at Kapulena.
The Hawaiian-produced macadamia established the well-known seed internationally. However, in 2006, macadamia production began to fall in Hawaii, due to lower prices from an over-supply.
Outside of Hawaii and Australia, macadamia is also commercially produced in South Africa, Brazil, California, Costa Rica, Israel, Kenya, Bolivia, New Zealand, Colombia, Guatemala and Malawi. Australia is now the world's largest commercial producer – accounting for roughly 40 percent of the approximately 100,000 tonnes of seeds in shell per year produced globally. To date, efforts to grow the macadamia commercially in Florida have not met with success, primarily as a result of low yield. However, the macadamia is a popular dooryard tree in Florida and efforts to select cultivars with better productivity are ongoing.
Assessment as to whether a macadamia has undergone sufficient drying to ensure the moisture content is low, can be undergone by dropping them in their shells from normal hand height onto a floor surface that is relatively hard and solid, e.g. concrete or tiles. Subsequent shaking and hearing the seed rattling inside indicates that it is loose from its shell, and can thus be cracked with a higher intact-seed-yield ratio. Seeds that do not rattle have not dried sufficiently to reduce the moisture content and allow it to shrink away from the shell. Periodically, a seed will not rattle regardless of its moisture content due to the orientation of the kernel.
To penetrate the husk's hard protective shell, a metal vise or hammer can be used to compress the shell until it lightly fractures, then the pressure is released and the seed is re-positioned to crack it along a different plane.
In Malawi, the macadamia tree was first introduced in tea plantations as wind shields in the low tea fields and the tea pickers used to roast the seeds in this style as a fatty snack.
Compared to other common edible seeds such as almonds and cashews, macadamias are high in fat and low in protein. They have the highest amount of monounsaturated fats of any known seed and contain approximately 22% of omega-7 palmitoleic acid, which has biological effects similar to monounsaturated fat. They also contain 9% protein, 9% carbohydrate, and 2% dietary fiber, as well as calcium, phosphorus, potassium, sodium, selenium, iron, thiamine, riboflavin and niacin.
|Nutritional value per 100 g (3.5 oz)|
|Energy||3,080 kJ (740 kcal)|
|Dietary fiber||8.6 g|
*Saturated fat: 12 g
*Monounsaturated fat: 59 g
*Polyunsaturated fat: 1.5 g
|Percentages are roughly approximated using US recommendations for adults.|
Source: USDA Nutrient Database
Macadamias are toxic to dogs. Ingestion may result in macadamia toxicosis, which is marked by weakness and hind limb paralysis with the inability to stand, occurring within 12 hours of ingestion. Depending on the quantity ingested and size of the dog, symptoms may also include muscle tremors, joint pain and severe abdominal pain. In high doses of toxin, opiate medication may be required for symptom relief until the toxic effects diminish. Full recovery is usually within 24 to 48 hours.
Macadamia oil is prized for containing approximately 22% of the omega-7 palmitoleic acid, which makes it a botanical alternative to mink oil, which contains approximately 17%. This relatively high content of "cushiony" palmitoleic acid plus macadamia's high oxidative stability make it a desirable ingredient in cosmetics, especially for skincare. However macadamias can cause severe allergic reactions in humans, as do many other seeds. These reactions can vary from a slight swelling of the lips, to an itchy throat or in the extreme, anaphylaxis. Caution should be used whenever around children or adults who have never ingested such seeds, or persons with known allergies to treenuts.  A skin test can also provide information about allergies while in a M.D./D.O.'s office who acts as specialist in allergens.
The trees are also grown as ornamental plants in subtropical regions for their glossy foliage and attractive flowers. Macadamia species are used as food plants by the larvae of some Lepidoptera species, including Batrachedra arenosella'.
Macadamia seeds are often fed to hyacinth macaws in captivity. These large parrots are one of the few animals, aside from humans, capable of cracking husk and shelling the seed. Nuts of the Arkin Papershell variety crack open more readily.
The macadamia tree is usually propagated by grafting, and does not begin to produce commercial quantities of seeds until it is 7–10 years old, but once established, may continue bearing for over 100 years. Macadamias prefer fertile, well-drained soils, a rainfall of 1,000–2,000 mm, and temperatures not falling below 10 °C (although once established, they can withstand light frosts), with an optimum temperature of 25 °C. The roots are shallow and trees can be blown down in storms; they are also susceptible to Phytophthora root disease.
A Macadamia integrifolia / M. tetraphylla hybrid commercial variety is widely planted in Australia and New Zealand; it was discovered by Dr. J. H. Beaumont. It is high in oil, but is not sweet. New leaves are reddish, flowers are bright pink, borne on long racemes. It is one of the quickest varieties to come into bearing once planted in the garden, usually carrying a useful crop by the fourth year, and improving from then on. It crops prodigiously when well pollinated. The impressive, grape-like clusters are sometimes so heavy they break the branchlet to which they are attached. In commercial orchards, it has reached 18 kg per tree by eight years old. On the downside, the macadamias do not drop from the tree when ripe, and the leaves are a bit prickly when one reaches into the interior of the tree during harvest. Its shell is easier to open than that of most commercial varieties.
A pure M. tetraphylla variety from Australia, this strain is cultivated for its productive crop yield, flavor, and suitability for pollinating 'Beaumont'.
A South African M. integrifolia / M. tetraphylla hybrid cultivar, it has a sweet seed, which means it has to be cooked carefully so that the sugars do not caramelise. The sweet seed is usually not fully processed, as it generally doesn't taste as good, but many people enjoy eating it uncooked. It has an open micropyle (hole in the shell) which may let in mould. The crack-out percentage is high. Ten year old trees average 22 kg per tree. It is a popular variety because of its pollination of 'Beaumont', and the yields are almost comparable.
A M. integrifolia / M. tetraphylla hybrid, this is a rather spreading tree. On the plus side, it is high yielding (commercially, 17 kg from a 9-year-old tree has been recorded), and the macadamias drop to the ground. However it is thick-shelled, and with not much flavor.
For thousands of years before European settlement, Australian Aborigines ate the native seed that grew in rainforests of eastern Australia. One of these seeds was called gyndl or jindilli (M. integrifolia), which was later borrowed as "kindal" by early Europeans. In New South Wales, the southern species is known traditionally as boombera (M. tetraphylla). In the Gympie area, seasonal feasts on 'boppal' (macadamia) seeds were held, especially at Mt Bauple (which was named after it).
Morris Arkin Backyard Horticulturalist - Arkin Papershell Macadamia