Pistachio

Pistacia vera
Pistacia vera Kerman fruits ripening
Salted roasted pistachio nut with shell
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Sapindales
Family:	Anacardiaceae
Genus:	Pistacia
Species:	P. vera
Binomial name
Pistacia vera L.

The pistachio (Pistacia vera L., Anacardiaceae) is a small tree native to some regions of Syria, Iran, Turkey, Greece, Turkmenistan, Pakistan, and Afghanistan, that produces an important culinary nut. Pistacia vera often is confused with other species in the genus Pistacia that are also known as pistachio. These species can be distinguished from P. vera by their geographic distributions (in the wild) and their nuts. Their nuts are much smaller, have a strong flavor of turpentine, and have a shell that is not hard. The word pistachio is a loanword from Persian via Latin, and is a cognate to the Modern Persian word پسته Peste.

History

The modern pistachio nut P. vera was first cultivated in Western Asia, where it has long been an important crop in cooler parts of Iran. It appears in Dioscurides as pistakia πιστάκια, recognizable as P. vera by its comparison to pine nuts.^[1] Its cultivation spread into the Mediterranean world by way of Syria: Pliny in his Natural History asserts that pistacia, "well known among us", was one of the trees unique to Syria, and in another place, that the nut was introduced into Italy by the Roman consul in Syria, Lucius Vitellius the Elder (consul in Syria in 35CE) and into Hispania at the same time by Flaccus Pompeius.^[2] The early 6th-century manuscript De observatione ciborum (On the observance of foods) by Anthimus implies that pistacia remained well known in Europe in Late Antiquity.

More recently, pistachio has been cultivated commercially in the English speaking world, in Australia, New Mexico,^[3] and in California where it was introduced in 1854 as a garden tree.^[4] David Fairchild of the United States Department of Agriculture introduced hardier cultivars collected in China to California in 1904 and 1905, but it was not promoted as a commercial crop until 1929.^{[3] [5]} Walter T. Swingle's pistachios from Syria had already fruited well at Niles by 1917.^[6]

Biology

The bush grows up to 10 meters (30 ft) tall. It has deciduous pinnate leaves 10–20 centimeters (4–8 inches) long.

Pistachio is a desert plant, and is highly tolerant of saline soil. It has been reported to grow well when irrigated with water having 3,000–4,000 ppm of soluble salts.^[3] Pistachio trees are fairly hardy in the right conditions, and can survive temperatures ranging between −10°C (14°F) in winter and 40°C (104°F) in summer. They need a sunny position and well-drained soil. Pistachio trees do poorly in conditions of high humidity, and are susceptible to root rot in winter if they get too much water and the soil is not sufficiently free draining. Long hot summers are required for proper ripening of the fruit.

The plants are dioecious, with separate male and female trees. The flowers are apetalous and unisexual, and borne in panicles.

The fruit is a drupe, containing an elongated seed, which is the edible portion. The seed, commonly thought of as a nut, is a culinary nut, not a botanical nut. The fruit has a hard, whitish exterior shell. The seed has a mauvish skin and light green flesh, with a distinctive flavor. When the fruit ripens, the shell changes from green to an autumnal yellow/red and abruptly splits part way open (see photo). This is known as dehiscence, and happens with an audible pop. The splitting open is a trait that has been selected by humans^[7]. Commercial cultivars vary in how consistently they split open.

Each pistachio tree averages around 50 kg of seeds, or around 50,000, every two years.^[8]

Cultivation

Commercially prepared pistachios in shells

The trees are planted in orchards, and take approximately seven to ten years to reach significant production. Production is alternate bearing or biennial bearing, meaning the harvest is heavier in alternate years. Peak production is reached at approximately 20 years. Trees are usually pruned to size to make the harvest easier. One male tree produces enough pollen for eight to twelve nut-bearing females. Harvesting in the United States is often accomplished by using shaking equipment to shake the nuts off the tree.

Pistachio nuts in and out of the shell

Pistachio trees are vulnerable to a wide variety of diseases (see List of pistachio diseases). Among these is infection by the fungus Botryosphaeria. This fungus causes panicle and shoot blight (i.e., kills flowers and young shoots), and can damage entire pistachio orchards.

In California, almost all female pistachio trees are the cultivar "Kerman". A sprig from a mature female Kerman is grafted onto a one-year-old rootstock. Male pistachios may be a different variety.

Bulk container shipments of pistachio nuts are prone to self-heating and spontaneous combustion because of their high fat and low water content.^[9]

Pistachio nut production in 2005 was 501 thousand metric tonnes.^[10]

Country	Share of 2005 production[10] (tonnes)
Iran	190 000
United States	140 000
Turkey	60 000
Syria	60 000
China	34 000
Greece	9 500
Italy	2 400
Uzbekistan	1 000
Tunisia	800
Pakistan	300
Madagascar	160
Kyrgyzstan	100
Morocco	50
Cyprus	15
Mexico	7
Mauritius	5

Uses

The kernels are often eaten whole, either fresh or roasted and salted, and are also used in ice cream and confections such as baklava or biscotti and cold cuts such as mortadella. American Midwesterners make pistachio salad, which includes fresh pistachios or pistachio pudding, cool whip, canned fruit and sometimes cottage cheese or marshmallows.^[11] In July 2003, the Food and Drug Administration (FDA) approved the first qualified health claim specific to nuts lowering the risk of heart disease: "Scientific evidence suggests but does not prove that eating 1.5 ounces (42.5g) per day of most nuts, such as pistachios, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease".^[12]

In research at Pennsylvania State University, pistachios in particular significantly reduced levels of low-density lipoprotein (LDL cholesterol) while increasing antioxidant levels in the serum of volunteers.^[13] In rats, consumption of pistachios as 20% of daily caloric intake increased beneficial high-density lipoprotein (HDL cholesterol) without lowering LDL cholesterol, and while reducing LDL oxidation.^[14]

In December 2008, Dr. James Painter, a behavioral eating expert professor and chair of School of Family and Consumer Sciences at Eastern Illinois University, described the Pistachio Principle. The Pistachio Principle describes methods of "fooling" one's body into eating less. One example used is that the act of de-shelling and eating pistachios one by one slows one's consumption allowing one to feel full faster after having eaten less.^[15]

Pistachios in shell

The shell of the pistachio is naturally a beige color, but it is sometimes dyed red or green in commercial pistachios. Originally dye was applied by importers to hide stains on the shells caused when the nuts were picked by hand. Most pistachios are now picked by machine and the shells remain unstained, making dyeing unnecessary except to meet ingrained consumer expectations. Roasted pistachio nuts can be artificially turned red if they are marinated prior to roasting in a salt and strawberry marinade, or salt and citrus salts.

Like other members of the Anacardiaceae family (which includes poison ivy, sumac, mango, and cashew), pistachios contain urushiol, an irritant that can cause allergic reactions.^[16]

The Chinese are the top pistachio consumers worldwide with annual consumption of 80,000 tons, while Americans consume 45,000 tons. Also, Russians (with consumption of 15,000 tons) and Indians (with consumption of 10,000 tons) are in the third and fourth places.^[17]

See also

• List of culinary nuts
• Cashew
• Pine nut

References

External links

 Chisholm, Hugh, ed (1911). "Pistachio Nut". Encyclopædia Britannica (Eleventh ed.). Cambridge University Press. 

• Germplasm Resources Information Network: Pistacia vera
• Pistachio Fun Facts
• Iran's Pistachio
• The Green Nut Website for Consumers and Media: http://www.thegreennut.org/
• The Western Pistachio Association Website for WPA U.S. Grower Members: http://www.westernpistachio.org/