Pistachio

Pistacia vera belongs to the family Anacardiaceae and is a small to medium-sized tree. The species is dioecious, with separate male and female trees. The tree grows up to 10 metres tall. The pistachio tree is native to Iran and Central Asia. The fruit is a drupe with a hard, cream-colored shell, and the seed inside has a mauve-colored skin and light green flesh. The fruit contains an elongated seed, which is the edible portion; the seed, commonly thought of as a nut, is a culinary nut and not a botanical nut. The leaves are deciduous and pinnate, 10 to 20 centimetres long, and the flowers are apetalous and unisexual, borne in panicles. The genus Pistacia belongs to the cashew family and contains at least eleven species, of which Pistacia vera is the only edible commercial one. Pistachio is a desert plant and is highly tolerant of saline soil.

Chemistry

The essential oil of the whole unripe fruits of Pistacia vera from Greece is very rich in α-pinene (54.6%) and terpinolene (31.2%). Twenty-one constituents were identified in it, and only three others exceeded 1%: limonene, 3-carene and β-pinene. In the fruit oil the (+)/(−)-α-pinene ratio is 99.5:0.5, that of limonene is 80:20 and that of β-pinene is 96:4, while α-terpineol was found only as the (−) form. The leaf essential oil has α-pinene (30.0%), terpinolene (17.6%) and bornyl acetate (11.3%) as major components, and thirty-three compounds were identified in it. In pistachio oils analysed by HS-SPME and GC-MS, d-limonene, α-pinene, 3-carene, β-myrcene, nonanal and α-terpinolene had the highest content. The major ones were α-pinene, octane and decane in samples from ultrasound-assisted extraction, and decane, nonanal and (E)-2-decenal in samples from Soxhlet extraction. Terpene concentrations were lower in the Soxhlet samples, while hydrocarbons and aldehydes were significantly higher. Long processing at high temperature is a key parameter in the formation of roasted compounds. The fruit oils of four related species (P. terebinthus, P. atlantica, P. lentiscus and P. palaestina) also contain α-pinene (3.8 to 15.6%) and terpinolene (0.1 to 6.9%), but in much lower concentrations than P. vera. α-Pinene and terpinolene have antibacterial and antifungal properties, and terpinolene has also been identified as an antioxidant.

Raw pistachios are 4% water, 45% fat, 28% carbohydrates and 20% protein. Oleic acid, at 52% of total fat, is the most common monounsaturated fatty acid, and linoleic acid makes up 30%. Palmitic acid makes up 10% of total fat and stearic acid 2%. A 100-gram reference amount provides 2,351 kilojoules (562 kcal) of food energy. Compared with other tree nuts, pistachios have less fat and food energy but more potassium, vitamin K, γ-tocopherol, carotenoids and phytosterols.

Production

In 2024 world production of pistachios in shells was 1.4 million tonnes, with the United States, Turkey and Iran together accounting for 87% of the total. In that year the United States produced 498,950 tonnes, Turkey 383,000, Iran 316,142, Syria 83,796 and China 78,986. In 2023, California produced 99% of the pistachios grown in the United States, with more than 428,000 acres devoted to the crop in 2022. Each mature tree averages around 50 kilograms of seeds, or around 50,000 seeds, every two years. Greece is one of the important pistachio-producing countries. Several years of severe drought in Iran from about 2008 to 2015 caused significant declines in production, and in 2011 anthracnose fungus caused a sudden 50% loss in the Australian harvest.

Uses

The kernels are often eaten whole, either fresh or roasted and salted. They are also used in Turkish delight candy, pistachio ice cream, traditional Persian ice cream, kulfi, spumoni, pistachio butter, pistachio paste, baklava, pistachio chocolate, pistachio halva, lokum, biscotti and cold cuts such as mortadella. Americans make pistachio salad, which includes fresh pistachios or pistachio pudding, whipped cream and canned fruit. Indian cooking uses pounded pistachios with grilled meats and in pulao rice dishes. In Greece the unripe whole fruits are used to prepare traditional spoon sweets. As a tree nut, the pistachio is considered a priority allergen that may induce allergic reactions in susceptible people.