The pistachio isn't really a nut at all. Technically, it is a "drupe," a fleshy tree fruit that contains a shell-covered seed. With pistachios we discard the fruit flesh for the tasty seed within. The opposite is true with other drupes such as stone fruits like peaches, cherries and apricots. With those, we eat the fruit flesh and leave the pits, for the most part, behind.
The pistachio belongs to a group of drupes called "culinary nuts" that include cashews and almonds. A real nut, also called a "true nut" or a "botanical nut," is not a fruit but rather a seed encased in a hard, woody shell. This group includes favorites such as hazelnuts, chestnuts and acorns. Nutty.
A Brief History
Sometimes it just takes a while to become an overnight success. Eaters have enjoyed pistachios since ancient times. Really ancient times: Archeologists have found evidence that they have been enjoyed for over seven thousand years. Originating in the Middle East, pistachios are believed to be one of the oldest flowering fruit trees. It took thousands of years for them to make the leap to what is now Europe. They were first introduced to Greece, and then later to Italy and what is now Spain by the first century AD. Religious conquests and expanding trade routes cemented pistachios' place in cuisines as far north as the Alps. But it wasn't until the Middle Ages that pistachios were introduced to England as a luxury item. And it wasn't until World War II that pistachios achieved snack status.
In the United States, pistachios were mainly imported until the mid-1970s when our domestic production found its feet. This was done was through the efforts of botanist William E. Whitehouse, who began importing and experimentally planting pistachio trees in the 1920s. Today, in California, where those original plantings were established, is responsible for 99 percent of our domestic production, with the other 1 percent coming out of Arizona and New Mexico. The production of pistachios has exploded over recent decades and we now produce over 80 million pounds of the nuts per year, enough to fulfill our domestic market and export product around the world.
- Before pistachios were grown domestically, they were often died red to hide the blemishes they incurred during transport from the Middle East.
- King Nebuchadnezzar had pistachios growing in the hanging gardens of Babylon.
- Because the nuts' shells open when ripe, they are uniquely susceptible to contamination by the carcinogenic aflatoxin, the toxic product of a mold that is common in a range of foods, including tree nuts. The Administrative Committee for Pistachios regulates 99.9 percent of the pistachios produced in the United States to prevent exposure to this potentially fatal toxin.
Pistachios are produced by Pistacia vera trees, deciduous trees which grow slowly to a height of twenty-five to thirty feet, with one or several trunks. The trees take five to eight years to fruit and then produce biennially. However, pistachio trees don't reach full maturity until the fifteenth or twentieth year. After that, the trees have a long fruiting life, as long as several centuries. In fact, ancient growers' wisdom dictates that you don't plant pistachio trees for yourself but for your children and your children's children.
Pistachio trees are desert plants that can grow in saline soils and are very tolerant of high summer temperatures. But they need a number of chilling hours - a period of cold weather - that is essential for the bloom and pollination of the trees. Trees that are not pollinated produce "blanks," or pistachio drupes that are hollow. They look like a fully mature fruit from the outside but have no nut inside.
Shifts in climate have impacted the pistachio crop in California. Warmer winters prevent the trees from getting the chilling hours they require to produce fruit. And, while trees are drought tolerant, complete lack of rainfall has impacted the trees' ability to thrive.
Harvest takes place anywhere from late August to early October. The nuts are harvested when the husk or hull covering the shell becomes fairly loose. Trees are shaken to release the nuts which fall into mechanical harvesters or onto tarp-covered ground. The outside fruit, or epicarp, must be removed within 24 hours to prevent staining. In large orchards this is done mechanically, but small scale growers load their freshly harvested pistachios into sacks and roll them around to knock the epicarp from the nut.
The pistachios are then dried either by laying them out in the sun for about two days or by giving them a twenty-minute spin in a commercial drying tank. The nuts are then roasted before being brought to market.
The California desert is an ideal climate for the trees, giving them the hot days, cool winters and abundant sunshine that make them thrive naturally. There are a lot of environmental pluses to pistachios:
Their deep tap roots allow pistachios to sip very lightly from irrigation sources. They require less water than other nuts, such as almonds, to grow.
In many orchards, IPM methods, such as owl boxes, are often used to control pests rather than pesticide spraying.
In sun-rich orchards, some growers are powering their processing facilities with solar energy.
Pistachio shells can be burned to generate electricity.
The hull can be used for cattle feed.
Nuts that fall outside of the canvas during harvesting are used as natural compost to feed the trees.
What to look for
On the tree, pistachios are reddish, wrinkled fruits that grow in heavy clusters reminiscent of a bunch of grapes. The husked fruit contains a thin, ivory-colored, bony shell that splits longitudinally along their sutures when mature. Inside the shell is the kernel - what we refer to as the nut. It is about one inch in length and a half-inch in diameter. The kernel ranges in color from yellowish to bright green, the more prized specimens being the more vibrantly hued.
Nutrition and Effects on the Body
Pistachios have twenty-five percent of the daily value for vitamin B6, fifteen percent of the daily value for thiamine and phosphorus and ten percent of the daily value for magnesium. They have fewer calories and more potassium and vitamin K per serving than other nuts. Pistachio nuts contain a substantial amount of fat - 15 grams - per ounce, the majority of which is unsaturated.
What to Do with It and Cooking
Pistachios can be eaten raw but are rarely available that way, as they are difficult to transport. Commercial pistachios are dried and roasted. You can find them salted and unsalted.
Pistachios are often eaten out of hand and are sold in their shells for snacking.
Shelled, unsalted pistachios are preferred for cooking. They are popular in sweet dishes such as ice cream, desserts and confections, particularly in Middle Eastern and Mediterranean cuisines. They are delicious in savory recipes as well. Try them in grain dishes and salads for a welcome crunch and rich, buttery flavor.
Stored in plastic bags, roasted pistachios will last for about a year in a cool dry place. Nuts go rancid over time, so it's important to rotate your pantry supply to ensure freshness. Only buy what you will eat within a few months if storing them at room temperature or freeze the nuts for longer storage. Always defrost in their sealed bag before opening to prevent condensation from forming on the nuts. Dampness can invite mold and fungus to contaminate the pistachios.
Pistachio and Goat Cheese Pesto
The nuts and cheese make this easy, meatless dish deliciously satisfying. You could use basil or other soft herbs such as cilantro in this recipe, but the peppery bite of the arugula does a super job of cutting the richness of the nuts and cheese. Serve it tossed with spaghetti or fettucine, which will pick up a nice coating of the sauce but still provide a good balance of pesto and pasta. You can also spread the pesto on crostini for a snack or cocktail nibble, perhaps topped with chopped tomato or some roasted vegetables such as beets or sweet potatoes.
1 cup shelled, unsalted pistachios (if using salted pistachios, eliminate the salt from the recipe)
¼ cup olive oil
4 ounces goat cheese, broken into chunks
Zest and juice from 1 lemon (from about one lemon)
Salt and freshly ground pepper
4-5 ounces arugula leaves, thick stems removed
1 pound strand pasta such as spaghetti or fettucine
Combine nuts, oil, cheese, lemon juice, a pinch of salt and a few grinds of pepper in a food processor or blender and puree until the nuts are ground and the mixture turns into a paste. Add the arugula and pulse until it is incorporated into the pesto. The pesto will be quite thick.
Boil pasta in salted water until nearly cooked through (a strand of pasta will still have a tiny white dot in the center). Drain pasta, reserving one cup of the cooking water. Return hot pasta to the pot, set over a low flame, add one cup of the pesto and a splash of the pasta water. Simmer the sauced pasta, tossing continuously, until all of the strands are well coated and the pasta is cooked through, adding more pasta water if it begins to dry out or more pesto to taste. Season with salt and pepper and serve.