In a nutshell, pistachios are a kind of edible seed with origins in the Middle East. They’re generally more expensive than other nuts because the pistachio tree can only be grown under certain conditions.
As delicious and valuable as they are, if you’re a regular pistachio consumer, you may be asking yourself, “Do pistachios go bad?”
Pistachios usually reach your shopping bag only after a thorough drying process, so they take a long time to turn rancid. Under the best storage conditions, they can last up to 1 year on the shelf and over 1 year in the fridge.
There are quite a few pistachio pitfalls that can cut their shelf life short. Let’s talk about the best way to keep pistachios fresh as long as possible.
How Long Do Pistachios Last?
The amount of time you can keep pistachios before they go bad depends a lot on how you store them. The packaging you buy them in also plays a factor and whether they’re roasted or raw and whether they’re whole or in pieces.
Pistachios Shelf Life
Raw pistachios will last about:
- 6 months to 1 year in the pantry
- Over a year in the fridge
- Over two years in the freezer
Roasted pistachios will last about:
- 3-6 months in the pantry
- 6 months to 1 year in the fridge
- 1-2 years in the freezer
Like most nuts, pistachios contain a lot of healthy unsaturated fats. When exposed to oxygen and heat, these can become oxidized and start to taste rancid.
How Long Are Pistachios Good For?
We found a bit of disagreement about ideal pistachio storage even across official government and university websites.
- The University of California says that pistachios last about a month at room temperature, 3 months in the fridge, and up to 1 year in the freezer.
- The USDA, however, says that you can keep pistachios at room temperature for as long as a year.
The most prodigious peer-reviewed study we perused on postharvest pistachio processing presented a perfunctory scale of the perfect pistachio protective packaging plan.
According to their scale, higher temperatures, relative humidity, and various other factors speed up pistachios’ deterioration.
Higher temperatures encourage a faster spread of harmful bacteria and biochemical reactions. Lower temperatures equal longer preservation, but there’s no simple cutoff date for fridge or pantry storage times.
We decided to use a broad scale of six months to a year for pistachio pantry storage and over a year for fridge storage. We hope it accurately reflects the slightly vague reality.
Roasted nuts tend to last about a quarter as long as raw nuts, and nut pieces usually last about half as long as whole nuts. Unshelled nuts typically last longer than the shelled version.
However, pistachio shells generally crack open when they ripen, all the official sources we read listed their shelled pistachios and unshelled pistachios shelf life as the same.
The USDA says that you can keep pistachios in the freezer for up to two years. After a long, frozen year, however, their nutritional content may begin to degrade.
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How To Tell If Pistachios Are Bad
Some good indicators of whether your pistachios have gone bad include:
- Brown discoloration
- Shriveled meat
- Foul odor
Start with a visual test. Good pistachios have nuts that are yellow or green. When they go bad, they slowly begin to change to an ugly dark brown.
Good pistachio nuts look full and rounded on the outside. Shriveled, dehydrated nuts probably mean your pistachios have gone rancid.
Unless you’re Alexander Fleming, don’t eat mold. If you notice your pistachios have grown a dusty coating of gray or black powder, it’s time to toss them.
Insects and other bugs can be delicious in an underground bunker. In the absence of an apocalypse, we recommend you throw away pistachios with a creepy-crawly infestation.
If your pistachios pass the visual test, move on to the smell test.
Rancid pistachios smell foul. Many people say they smell like nail polish remover or wet paint. If it smells bad, toss out your pistachios.
The touch test doesn’t generally work on pistachios. Soft pistachios aren’t necessarily bad.
They might have absorbed some moisture from the air if they were left in humid conditions. You can actually recover their crispy crunchiness by toasting them in your oven for about 10 minutes.
Can Expired Pistachios Make You Sick?
The fats in pistachios begin to break down into rancid fatty acids if you leave them exposed to air, heat, or light for too long. This is a gradual process that can take years to complete.
The more the pistachio’s fats have broken down, the worse they’ll taste and the sicker they can make you.
Eating a few barely stale pistachios probably won’t taste too bad or make you too sick right away. A steady diet of stale pistachios could lead to problems with digestion or more long-term adverse effects.
If you eat a bunch of pistachios that taste sharp and unpleasant, they can irritate your digestive tract, especially if you have a delicate stomach lining.
The broken-down unsaturated fats will probably upset your stomach and give you gas. Exceptionally rancid pistachios can make you nauseous and may even give you diarrhea.
How To Store Pistachios
To store your pistachios in the pantry:
- Seal them in an airtight container.
- Keep them away from heat and light as much as possible.
- Keep the relative humidity around 65-70%.
- Don’t store them around strong-smelling foods.
If you buy properly-processed pistachios and never open the sealed bag, their expiration date will usually come in around two years.
Processed pistachios last longer because they usually have a lower fat content and have been through a carefully-calculated drying process.
Regular pistachios exposed to regular air need a bit more care to ensure they last as long as they can. Good pantry conditions for pistachios are ones that induce as little change as possible in the quality of their unsaturated fats.
This means you should keep your pantry between 65-70% relative humidity and never let the temperature hit more than about 70 degrees Fahrenheit.
Higher relative humidity won’t necessarily make your pistachios turn rancid, but it can make them go soft. If there’s excess moisture in the air, your extremely dry pistachios may absorb some and lose their crispiness.
You don’t need to keep your pistachios in the fridge unless you’re planning for long term storage. They’ll keep for a year or more in the fridge, but unless you somehow got your hands on the last pistachios on earth, you’ll probably have eaten them all by then.
Whether you keep your pistachios in the fridge or pantry, the less air that reaches them, the better. Plastic is more porous than glass, so using an airtight glass container will let less air inside than a plastic container with a lid.
Researchers believe that a vacuum-sealed nylon container makes the best pistachio packaging if you really want to get picky.
Nuts love to absorb smells from other foods, and pistachios are no exception. If you want your pistachios to still taste like pistachios months later, don’t keep them in the vicinity of other foods with strong odors.
Pistachios are a rich source of thiamine and the highly sought-after B6 vitamin. They’re usually eaten dry, which helps keep much of the natural rotting process at bay.
You can prevent pistachio pain in your stomach by checking for discoloration, shriveling, mold, bugs, and bad smells before popping one into your mouth.
Keep them isolated from air, heat, and light as much as you can, and they may last for a year or more.
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