Why Do Some Pistachios Taste Bad?

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Pistachios are the perfect snack, especially when roasted and salted and full of flavor. They are a healthy way to get some protein while on the go, in fact they are so good I find myself often wanting to eat the whole bag.

However, there seems to be a bad pistachio or two in each bag, which has an unpleasant, bitter flavor, and you might be worried about whether these are okay to eat or not.

Why Do Some Pistachios Taste Bad?

While most of the pistachios in a bag taste fine, the one or two that taste bitter or unpleasant could be because those pistachios have started to go rancid and off. It could also be because they are unripe. 

Read on to find out more about those bitter and unpleasant pistachios you sometimes come across, and whether or not they are okay to eat.

Why Do Some Pistachios Taste Bitter?

There are two reasons why pistachios might taste bitter and unpleasant. The first is that unripe pistachios can often have a bitter flavor, which is a result of the higher tannin content in the unripe pistachios.

Unripe pistachios have a bitter, yet mildly-sweet taste to them. How bitter the pistachios are will depend on how unripe they are, but there should still be some sweetness to them, which takes away some of the unpleasantness.

The other reason that pistachios might have a bitter or unpleasant flavor is when they have begun to spoil and are going rancid. Pistachios have a high oil and fat content, and this means that they can spoil and become rancid.

This does not happen overnight, but if left for too long, pistachios can spoil and take on a sour, bitter, and unpleasant taste to them.

Are Bad-Tasting Pistachios Safe to Eat?

If pistachios are bitter because they are unripe, there isn’t much danger in eating them, and it will mostly just be a bad taste experience.

However, it does become a little riskier when you eat a pistachio which tastes bitter because it has gone rancid. It is never a good idea to eat rancid food, and while it might be fine if you have mistakenly eaten one or two rancid pistachios, there is a risk it could make you sick.

How rancid the pistachio is will also determine how dangerous it might be for you to eat, as the bacteria content would vary between a newly spoiled pistachio and one that has been spoiled for quite some time.

Signs That Pistachios Have Spoiled

It might be difficult to tell an unripe pistachio from a ripe one, but there is little danger in eating unripe pistachios.

It does help however to know how to tell whether a pistachio has gone rancid and is off, so you can hopefully avoid eating these.

Here are the signs to look for that a pistachio has spoiled:

Sour Smell

If a bag of pistachios has started to spoil, you should be able to notice a sour, off smell in the packet. If you open a bag of pistachios and notice a smell different from what you would expect, then you should discard it straight away.

It is harder to tell whether a single pistachio has spoiled with smell alone, but if there are other signs that the pistachio might be off, you can try to smell it to pick up on any sour notes.


A pistachio that has begun to spoil will have some discoloration. The pistachio will not be green and bright, and it will begin to dull and turn gray.

In cases where the pistachios have been left for some time to go off, they might even begin to develop mold, which could be gray, black, or white spots on the pistachio or in the bag they are stored in.

Shriveled And Dried

Along with a change in color, pistachios might begin to shrivel and dry up. They will look quite unappetizing and smaller in size than what they should.

Shriveled and dried-up pistachios, when they display other signs of spoiling, should be discarded.

How Long Do Pistachios Stay Fresh?

Pistachios, when stored in airtight packaging, in a cool, dark environment, will keep fresh for up to 6 months. 

The shelf life of pistachios can be extended further by keeping them in the fridge, where they will be able to last for up to a year.

If you are wanting your pistachios to last even longer than this, then you could place them in a freezer, in an airtight container or plastic freezer bag, and keep them frozen for up to a year and a half.

Keep an eye on the best-by date, or the expiry date, on the packaging of the pistachios, to make sure you can use them before they spoil.

Do Shelled Or Unshelled Pistachios Last Longer?

Unshelled pistachios last longer than shelled pistachios, but only for a few weeks more. This is because the shell protects the pistachios from humidity and air, which could cause them to turn rancid quicker.

Once the pistachios are shelled, they are left open to moisture and humidity and will begin to go rancid sooner.

However, the difference isn’t too noticeable if you eat the pistachios soon after buying them, and you should still store them properly in a dark, cool environment.

Why Do Some Pistachios Taste Bad?

Nobody wants their pistachio snack ruined by a bitter or unpleasant pistachio, but it does happen, and there are two reasons why it might.

The first reason why you might have a bitter pistachio in your pack is that it has not ripened enough yet, and it still contains a high amount of tannins. However, the pistachio will still have a slightly sweet taste to it.

The other reason is that the pistachio has started to go rancid, and this is because it has a high fat and oil content, and it begins to spoil after some time. Rancid pistachios have a bitter, unpleasant taste, and are not fun to eat at all.

Check for signs of spoiling with the pistachios you are about to eat, to make sure you only eat fresh, ripe pistachios.

Related Questions

Should pistachios be kept in the fridge?

Pistachios do not have to be kept in the fridge, but you can store them in the refrigerator to extend their shelf life by a few months.

In the fridge, the pistachios should be kept in an airtight, sealed container.

Is it better to eat roasted or raw pistachios?

There is not much difference between raw or roasted pistachios when it comes to nutrient content, as it is pretty much the same. It will mostly depend on the type you prefer to eat, whether roasted and salted or not.

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