Nut of the Week - Pistachios

Pistachio nuts in and out of the shell

The pistachio, Pistacia vera in the Anacardiaceae family, is a small tree originally from Persia (Iran), which now can also be found in regions of Iraq, Syria, Lebanon, Turkey, Greece, Tunisia, Kyrgyzstan, Tajikistan, Turkmenistan, India, Pakistan, Egypt, Sicily, Uzbekistan, Afghanistan, especially in the provinces of Samangan and Badghis, and the United States, specifically in California. The tree 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.

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. 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 Jylgyndy Forest Reserve, a preserve protecting the native habitat of Pistacia vera groves, is located in the Nooken District of Jalal-Abad Province of Kyrgyzstan.

The bush grows up to 33 ft tall. It has deciduous pinnate leaves 4–8 inches long. 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. This is known as dehiscence, and happens with an audible pop. The splitting open is a trait that has been selected by humans. 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.

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.

Iran, Iraq and Tunisia are the major producers of pistachios. 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 and in Greece is often accomplished by using shaking equipment to shake the nuts off the tree. After hulling and drying, pistachios are sorted according to open mouth and closed mouth shell. Sun drying has been found to be the best method of drying. Then they are roasted or processed by special machines to produce pistachio kernels.

The kernels are often eaten whole, either fresh or roasted and salted, and are also used in ice cream, pistachio butter, pistachio paste[18] and confections such as baklava, pistachio chocolate, pistachio halva or biscotti and cold cuts such as mortadella. Americans make pistachio salad, which includes fresh pistachios or pistachio pudding, whipped cream, canned fruit and sometimes cottage cheese. 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".

China is the top pistachio consumer worldwide with annual consumption of 80,000 tons, while the United States consumes 45,000 tons. Russia (with consumption of 15,000 tons) and India (with consumption of 10,000 tons) are in the third and fourth places.

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. 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.

Consuming unsalted, dry roasted pistachios prevents any addition of unwanted fats and additional sodium in the diet that may affect cardiac health adversely and increase hypertension.

Human studies have shown that 32-63 grams per day of pistachio nut can significantly elevate plasma levels of lutein, alpha-carotene, beta-carotene, and gamma-tocopherol.

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 shelling and eating pistachios one by one slows one's consumption, allowing one to feel full faster after having eaten less.

The empty pistachio shells are useful for recycling in several ways. If unsalted, the shells need not be washed and dried before reuse, but washing is simple if that is not the case. Practical uses include as a fire starter just as kindling would be used with crumpled paper; to line the bottom of pots containing houseplants for drainage and retention of soil for up to two years; as a mulch for shrubs and plants that require acid soils; as a medium for orchids; and as an addition to a compost pile designed for wood items that take longer to decompose than leafy materials, taking up to a year for pistachio shells to decompose unless soil is added to the mix. Many craft uses for the shells include, holiday tree ornaments, jewelry, mosaics, and rattles. Scientific research indicates that pistachio shells may be helpful in cleaning up pollution created by mercury emissions.