How Pistachio Nuts Are Harvested And Processed?

Historically, many farmers were put off growing pistachios due to their high processing costs. Today, the number of commercial growers is increasing due to a changing climate and soil nutrient depletion that is tolerated by pistachio trees, high market value, and booming pistachio demand from consumers. But just how are pistachio nuts harvested and processed, and what is all the fuss about?

How Are Pistachios Harvested & Processed?

Before we get to enjoy some delicious pistachios, first they must be harvested and processed. 

Harvesting Pistachios

Pistachios are harvested from late summer through to fall when the shells naturally split and the fruits are mature.

Harvesting has to happen in a relatively short time window, as the nuts splitting allows contamination to occur. 

Because the nut shells are open, it’s important they never touch the ground and contaminate the nut with dirt, making it a health risk.

Getting pistachios out of your tree at home requires shaking the branches and catching the nuts on a clean sheet as they fall.

Much the same method is used in commercial pistachio picking, only the shaking is done by a device fixed to a tractor or telescopic, or in larger operations, a purposefully designed vehicle. 

Smaller devices have an arm that fixes around the upper trunk of the tree and vibrates it by shaking very rapidly in relatively small, fast movements. 

Below the shaking arm, there is a clever bit of kit which opens out rather like a fan but is shaped more like an upside-down umbrella. This encircles the tree and captures the nuts as they fall, funneling them into a receptacle.

The larger machines work in tandem and incorporate the shaking mechanism and the capture bed in a single unit. A large auger moves the nuts into waiting trailers to be transported away.

Equipment such as this doesn’t come cheap, although it can now be purchased in a range of sizes, from a small, single-operator device to much bigger versions suitable for large-scale growers.

Pistachio Processing

One of the main reasons farmers are put off growing pistachios is the amount of processing they require. Many smaller-scale farms fear that the costs of equipment are just too great to make it financially viable. 

However, as the popularity of pistachios continues to rise, more small-scale farmers are coming together to form processing cooperatives, so the cost of equipment and labor can be split between many to ease the financial burden.

Larger commercial operations process their pistachios using huge machines in a processing plant.

Pistachios have a tendency to go rancid quickly. They grow mold spores that are dangerous to health, so speedy processing is required to keep them in top condition.

1. First, they are put through grinders that remove the external fleshy husk from the outside of the nuts.
2. They move on to a machine that shakes the nuts to remove any debris, including the husk remnants, twigs, stones, etc.
3. Next, they are sieved to further remove contaminants.
4. The nuts now go into a bath that floats any which are not filled (blanks) to the top. The good nuts sink to the bottom.
5. A special needle machine sorts out the open nuts from the closed ones. This is then backed up by human sorters who visually check the nuts coming out of the machine on a conveyor belt and remove any that are not good.
6. In hot countries, the nuts are spread out in the sun to dry, which takes around two days. More commonly, they are put into large drying machines that dry the nuts in around 20 minutes to two hours, depending on size.
7. In large-scale operations, a sample from each batch is sent to a laboratory for testing. This is to ensure there is no fungus present which is important, as the fungus can produce aflatoxins which are believed to be carcinogenic and hazardous to health.
8. Once a batch of raw nuts has passed the test, it’s ready for the next stage. If the salting and roasting are to be done in another country, the nuts will be vacuum sealed and shipped.
9. On arrival at their destination, further cleaning happens to ensure there are no contaminants, such as small twigs or tiny stones. This is done by a machine that shakes the nuts while blowing air through them simultaneously. The air removes any lightweight debris from the nuts, while the shaker drops stones into a receptacle below.
10. Salting is the next process. This is done by putting about a ton of nuts into a salt bath with just over 26 gallons of salt water. The machine operates rather like a cement mixer to thoroughly combine the nuts and saline together, taking around 15 minutes.
11. Next, the nuts move on to the roasting ovens, which are set to 320°F. Here they are roasted for about 10 minutes to develop their delicious flavors.
12. Finally, the nuts are weighed and packaged, ready to be shipped off to the stores ready for sale.

In this video, you can see how pistachios are harvested and processed by a small commercial grower, proving that it can be done on a smaller scale:

https://www.youtube.com/watch?v=ABjHFy7u1Ek

Are Pistachios Edible Straight From The Tree?

Yes, pistachios are edible straight from the tree, but there are a few things to keep in mind. Firstly, you’ll need to get rid of the outer layer called the “epicarp.” This can be quite tough. 

Small farms use commercial potato peelers to remove this husk so a good-sized batch can be done together. 

Raw pistachios are not particularly digestible, and some believe you can increase their nutritive value by soaking them in water for around 12 hours. There are conflicting opinions on this.

Remember not to eat pistachios that have fallen onto the ground, as they can easily become contaminated.

Because the nuts quickly go rancid and become dangerous to your health, only eat them when they are fresh and don’t keep them hanging around.

Surprisingly, raw pistachios don’t really have any more health benefits than cooked ones, as the cooking process does not appear to damage the nutrients they hold, provided they are not cooked for too long or at too high a heat.

Why Are Pistachios No Longer Dyed?

Believe it or not, pistachio nuts used to be dyed red!

Before the 1970s, pistachios were imported into the United States from Asia and the Middle East. 

Harvesting methods at that time meant that they often had unsightly stains and blemishes on the shells, so the producers would dye them a bright red to try and hide these imperfections.

The belief was that this would make them more appealing to consumers.

Luckily this practice all but ended in the 1980s as the number of pistachios grown in the US increased. 

Better harvesting methods meant the nuts didn’t have stained shells and so there was no need to dye them. 

You can still buy red pistachios as a kind of nostalgic treat from some suppliers. 

How Do They Take The Shells Off Pistachios?

When pistachios ripen, the shell naturally opens. Removing the shells from slightly under-ripe nuts, where the shell has remained closed, is a delicate art if you don’t want to damage the nut inside when breaking the shell. 

In factories, the nuts are put under pressure that is just sufficient to crack open the shell but not so much that it destroys the flesh of the nut.

Smaller operations use ingenious devices that comprise of a large cog that turns against a metal plate, and a side-mounted piston. 

The cog turns continuously, picking up a single pistachio in each of its teeth. As each nut draws level with the piston, it fires, sending a bolt to hit the nut at exactly the right pressure to crack open the shell without damaging it.

At home, you can place your nuts into a clean fabric bag or on a chopping board under a kitchen towel and tap them with a rolling pin. You’ll need to work out just how much force is needed, but it will always be impossible to get it right every time.

Conclusion

As the value of the pistachio market continues to rise, more and more small farmers want a piece of the pie.

This is being facilitated in a number of ways:

Smaller, more affordable machinery that allows a single person to harvest the nuts, and cooperatives that can set up small-scale processing plants together, to benefit all the local producers.

Pistachio nuts do require a considerable amount of processing before they can be sold to the consumer. Even if you want to prepare them for yourself at home, they will need quite a bit of time and effort.

• Nuts must be shaken from the tree without touching the ground
• Have the outer husk removed
• Be separated from all debris and contaminants
• Have the unfilled nuts removed
• Be checked for splitting
• Have salt applied, which is optional
• Go into the ovens to be roasted
• Get placed into their packaging
• Be stored safely

Nuts can be enjoyed raw but have a different flavor than cooked ones. There is no real nutritional advantage to eating them raw except for the loss of vitamin C. In fact, they are overall more indigestible in their raw state. 

To discover more about growing and caring for pistachio nuts and to read other informative articles on farming and animals, take a closer look.