Pistachio

Pistacia vera is a small, deciduous tree, 5 to 10 metres tall, with pinnate leaves and separate male and female trees. The fruit is a drupe with a thin husk, and inside is a hard, cream-coloured shell that splits open with a faint popping sound when ripe, revealing a kernel with a purplish skin and bright green flesh. The kernel has a delicate, slightly resinous, sweet flavour. Pistachios belong to the same family as cashews, mangoes and sumac. The tree tolerates drought, heat and poor soil, but needs cold winters to flower well.

Wild pistachio species are native to Central and Western Asia, with Iran, Afghanistan and Turkey as historic centres of the crop. Today Iran, the United States, particularly California, and Turkey are among the major producers, followed by Syria, China and Greece, where the nut is known as Aegina pistachio. Orchards occupy semi-arid areas with hot dry summers. Trees take about seven years to begin producing and may bear for many decades, with alternate-year crops being common.

Archaeological evidence suggests that pistachios were eaten in the Near East thousands of years ago. Tradition says they were grown in the legendary Hanging Gardens of Babylon, and the nut was known to the ancient Persians, who prized it as a luxury. Classical writers described it as a delicacy, and it spread across the Mediterranean through trade.

Pistachios arrived in the United States in the nineteenth century, but commercial production did not take off until the 1970s in California, helped by research on improved varieties. Red-dyed pistachios were once sold to disguise stains from old methods of harvesting; the dye is less common today. Iran and the United States now lead the world trade, and pistachio flavour is central to dishes from baklava to gelato and Italian mortadella.

Pistachios are eaten as a snack, roasted and salted in the shell, and shelled for use in baklava, halva, nougat, ice cream and biscotti. They are ground into pistachio paste for pastries, folded into pilafs and stuffing, used to crust fish or meat, and sprinkled on yoghurt, salads and desserts. Their green colour makes them popular in confectionery. Unshelled pistachios encourage slower eating, which may help with portion control. Raw kernels can be blanched by soaking briefly in hot water so the skin slips off.

Pistachios offer protein, fibre and unsaturated fat, plus vitamin B6, thiamine, copper, phosphorus and potassium. They also contain lutein and other carotenoids, uncommon among nuts. Studies on regular pistachio intake in adults have reported modest improvements in some blood lipid measures, but sample sizes are small. A typical portion is a small handful. Salted and flavoured varieties can add a lot of sodium, so unsalted nuts are a better choice for regular eating.