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Can Walnuts Go Bad?

You’ve found an old pack of walnuts in the back of a cupboard. The nuts look quite alright, but you’re not sure if you can eat them. Can walnuts go bad?

You probably forgot about it when you were reorganizing the pantry. Now that you “found” it, you noticed it’s past its date. How long are walnuts good for after their expiration date?

To get answers to these two, and other questions related to storage and shelf life of walnuts, read on.

Bunch of shelled walnuts
(credit: Tom Hermans)

Can Walnuts Go Bad? How To Tell If They Are Bad?

No matter if it’s walnuts, pistachios, or hazelnuts, all nuts can go bad. That happens mainly for two reasons:

  • storing walnuts for too long in conditions not fit for long-term storage
  • bad storage conditions

Let’s focus on the spoilage of walnuts. We’ll discuss storage a bit later.

If your walnut kernels are moldy or shriveled and dried out, it’s time for them to go.

More often than not, the kernels look quite alright. If that’s the case, you should check for rancidity. Rancidity in walnuts shows in a couple of ways:

  • nutmeat being much darker than it usually is (for English walnuts, in black walnuts it’s always quite dark)
  • paint-like smell, or anything that reminds you of rancid fat
  • harsh, bitter taste

Either of these means the kernel is rancid, and you should get rid of it.

Pile of unshelled walnuts
(credit: Ashkan Forouzani)

If you have a big package of shelled walnuts, you probably don’t have the time to check each piece separately. In this case, it’s probably best to pick a dozen kernels and decide what to do with the package based on these.

For unshelled walnuts, they usually keep quality for longer, and chances are that some of the kernels will be quite alright even in old nuts. Again, crack a bunch with a nutcracker, check what’s inside, and move forward based on what you find.

Please note that walnuts go rancid quite easily. They have quite a lot of polyunsaturated fatty acids (ND) that oxidize easily (HL).

Nuts and a nutcracker
(credit: O12)

How Long Do Walnuts Last?

Let’s start with cold storage. Pretty much every reliable source agrees that if refrigerated, walnuts can last about a year, and two years if frozen (FK, UCANR). But if fridge and freezer space comes at a premium, you’d rather keep them in the pantry, wouldn’t you?

Just like with pistachios, there’s a lot of conflicting information on pantry storage. Some sources (FK) say it’s super limited, like 2 to 4 weeks for both shelled and unshelled. The guidelines that come from the University of California (UCANR) are a bit more relaxed, and state that in-shell walnuts last four months, while shelled ones three months in the pantry.

For me, the latter estimate is much closer to the truth, especially when it comes to unshelled walnuts. The shell isolates the kernel from temperature changes, air, and light, all three factors responsible for rancidification (WIKI).

If you’re buying packaged walnuts, check the label. Even though the date on it is just an estimate, it gives you an idea of what to expect. For shelled walnuts, don’t expect much more than a couple of months in good quality past that date. That is if you take good care of storing those nuts.

Speaking of which…

Shelled walnuts on a baking pan
(credit: Jade Wulfraat)

How To Store Walnuts

As you probably already know, there are three locations to choose from: the pantry, the fridge, and the freezer.

Many places recommend always going with cold storage (W), no matter if walnuts are shelled or not. And what’s sure it that they last the longest in such conditions. In short, if you need to store walnuts for who knows how long, freezing is the way to go.

But if you’re like me, and buy enough walnuts for a month or two tops, the pantry or a cabinet in the kitchen are usually good enough. Assuming that you don’t live in the tropics, of course. If you do live in a hot climate, go with the fridge.

Now that we covered the places let’s discuss the how.

Walnuts and fruits on a cutting board
(credit: Roberto Patti)

I already mentioned that keeping walnuts from air, temperature changes, and light helps them retain quality for longer. If the nuts are already shelled, you need to take care of those on your own. The easiest way to go about that is by keeping the nuts in an airtight container. Sometimes walnuts come in resealable bags, and if that’s the case, you can use them instead.

If you’re going with room temperature storage, put the nuts away from sunlight. A dark cabinet is your best choice. Just don’t but it in the back, so you forget about it in a couple of minutes only to “find” in a few months.

For me, I usually buy unshelled walnuts in bulk, keep them in a dark spot and shell as needed. This way, they don’t take space in the fridge, and the quality is never an issue.

Walnuts and apples
(credit: Boba Jaglicic)

In a Nutshell

  • toss away moldy, dried, or rancid walnuts
  • unshelled walnuts keep much better than shelled ones, so if you want to stock up, go with unshelled nuts and shell as needed
  • cold storage (fridge, freezer) is best for long term storage
  • room temperature is okay for short term, just make sure to use an airtight container if the nuts are shelled