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How long do Walnuts last? Can they go bad?

It is so easy to end up buying literal tons of walnuts when they go on sale. They’re so expensive most of the time that when we see a bargain we can get totally sucked in. But, what do you do when you end up with way more than you could possibly use in a short time?  A thought could be to start using them in recipes (they made a perfect topping with tomatoes on polenta bowls, a crust layer for banana cream pie jars or a cookie dough ingredient) or, if you do, discover their full potential as a substitute to plenty of recipe ingredients. Thankfully, there are also options out there that don’t involve wolfing down handfuls and racing against time to consume them all before they go off.

The thing about walnuts, however, is that they have such a high fat content that their expiry date can vary dramatically depending on how they’ve been stored. In this sense, not even the printed date on the package shouldn’t be taken as gospel. How you store them could add a year to this. Similarly, you could also accidentally end up shortening the lifespan of your walnuts if you’re not careful. So, without further ado, here are some quick and easy tips to make sure you never have to throw out rancid walnuts again!


The Best Way to Store Walnuts

Walnuts, like many other nut varieties, are very high in fat. This fat can easily go rancid and cause the nut to taste incredibly bitter if not stored correctly. In short, the things that you need to keep away from the nuts are the usual elements that damage food products. These are moisture, air, and heat. Naturally, when you buy walnuts that are still in the shell, they have an extra layer of protection against these harmful elements. But, very few of us buy our nuts this way now. After all, why would you when there’s conveniently packaged and already opened ones everywhere? However, if you can buy them this way, they will reward you by keeping for longer.

Walnuts in shell

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Walnuts in the shell are wonderfully low maintenance. They don’t require refrigeration as they pretty much take care of themselves. Essentially, all you really need to do is to keep them out of direct sunlight to stop the shell itself heating up. This can be achieved pretty much anywhere in the kitchen or in the pantry and then you simply crack only enough that you plan to use in the next few days.

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Shelled walnuts

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Shelled walnuts behave totally differently to their whole counterparts. This is in no small part due to the fact that as soon as they are shelled, they are oxygen exposure takes action. As a result, as soon as the seal is broken on the packaging, the best move is to reseal and put them in the fridge, or in the freezer if you aim to keep them for extended periods and ideally use a vacuum food bag. In either case, make sure that they are totally sealed before putting them away as they can absorb other odors from nearby foods. For example, if there is an onion and some loose walnuts in the fridge, you will notice that those walnuts will eventually end up tasting of onion. We’re fairly sure no one wants that, right? An extra tip: if you intend to use chopped or ground walnuts as part of a recipe, process them as you need them rather than in advance.


How Long Do Walnuts Last?

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Unshelled walnuts

Unshelled walnuts can last for an incredibly long time if stored out of the way of direct sunlight. In fact, it is not uncommon for these nuts to last from one harvest to the next – a full year! However, this may not be the case across the board. Some shells will have been penetrated by either bugs or air, but thankfully these will be easy to differentiate from the others. They will either be dried, shriveled, moldy, or largely absent. In any of these cases, the best call is to get rid of that particular nut and to keep cracking. Naturally, the longer you leave them aside, the higher the chance that a few will be bad.

Shelled walnuts

Shelled walnuts require much more care and caution than their shelled counterparts. When in their unopened package, they can last as long as their expiry date indicates. Out of the package, the situation is totally different. Due to their high fat content, walnuts go rancid relatively quickly once exposed to the elements. Even when stored absolutely perfectly, one can only expect them to last up to four weeks in the pantry. Because of this, it is much better to transfer your walnuts into a sealed container as soon as they have been opened. When these have been placed into the fridge, that shelf life can be extended as far as 6 months. However, as time goes on you may notice that one or two are beginning to turn bad before the others.


Signs That Your Walnuts May Have Gone Off

walnuts mold bad

Walnuts can be quite tricky in this regard as they may not give away their status straight away. There’s several different ways that walnuts can go bad, some of which are obvious and others are not. In the case of walnuts that are still in the shell, the easiest way to tell if they have gone off is to look at the shell itself. Is the shell shriveled and shrunken? If so, the chances are very high that the nut itself is also in bad condition. You can safely save yourself the effort of opening these ones and just chuck them out instead.

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How Long Does Bread Last? Can It Go Bad?
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Spoiled walnut with apparent signs of mold


The next sign you should be on the lookout for are subtle visual signs. Generally, these come in the form of discoloration or mold. If you notice either of these, there is no point moving on to a taste test as they have definitely seen better days and should be discarded.

However, possibly the most annoying thing about walnuts is that some gone off ones will still pass through these tests undetected. These ones can then go on to absolutely ruin whatever dish they come into contact with. So, how do we stop this from happening? Simply give them a sniff. If the naturally rich and nutty aroma has been replaced by a bitter and almost oily scent, it is time for them to go! Sometimes, the occasional nut will still get beyond this test and reveal itself to be bitter, but at this point, you have done everything you can. Such instances are quite rare too, so don’t worry too much – rancid nuts generally won’t have any ill effects on your health.


Should Walnuts be Refrigerated?

Once a package of walnuts have been opened, or the shell has been removed, the best course of action is to refrigerate them straight away in a sealed container. By doing so, you can extend their shelf life from 2-4 weeks to a whopping 6 months! This lifespan can also be extended even further by freezing if you see fit to do so. In fact, they should retain their quality for up to two whole years. In the case of walnuts that are still in their shell, there is no point in refrigerating them as they will last for up to a year in the pantry and away from direct sunlight.


Walnut Storage, Sell-by Dates, and Other Related Questions

How long do walnuts last after packaging?

Walnuts are one of those rare products that last pretty much exactly as long as the package indicates, provided they haven’t been opened and they have been stored correctly.

What makes walnuts go bad?

Due to their high-fat content, walnuts don’t deal too well with too much exposure to harsh environments. By these, we mean the usual elements such as too much air, moisture, direct sunlight, or heat. All of these can be avoided using our storage tips above.

Are unshelled walnuts better?

Though unshelled walnuts take considerably more effort to prepare when it comes time to put your recipe together, the positives outweigh the negatives. They take so little effort to store and much longer to go bad.

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