Walnuts that are still shelled can keep their freshness for up to 12 months. You can store them in your pantry, fridge or freezer with the same shelf life. Walnuts have a fair shelf life, which lasts up to 3 months with the shells set at room temperature. When the shells are removed, the nuts oxidize much faster and only stay fresh for a couple of weeks.
Shelled walnuts are kept for at least half a year at room temperature and more than a year in the refrigerator. On the other hand, shelled walnuts last at least 3 months in the pantry and more than 12 months in the refrigerator. Shelled walnuts require much more care and caution than their shelled counterparts. When they are in their unopened package, they can last as long as their expiration date indicates.
Outside of the package, the situation is totally different. Because of their high fat content, walnuts turn rancid relatively quickly once exposed to the elements. Even when stored perfectly, they can only be expected to last up to four weeks in the pantry. Because of this, it is much better to transfer the nuts to a sealed container as soon as they have been opened.
When placed in the fridge, the shelf life can be extended up to 6 months. However, as time goes on, you may notice that one or two are starting to get bad before the others. How long do shelled walnuts last? Shelled walnuts won't last long. They can usually last up to a month in the pantry, or maybe two months if stored in an airtight bag with very little air inside.
Speaking of shelled walnuts, they become vulnerable to moisture and oxygen as soon as they are shelled. As I mentioned in the spoilage section, walnuts are prone to going rancid, thanks to their nutritional profile. Everyone, including me, agrees that going with the fridge or freezer is the best option if you want nuts to last as long as possible. Similarly, you could also end up accidentally shortening the shelf life of your nuts if you're not careful.
It's nothing fancy, but you avoid most of the negative changes in nut fats and keep vitamin loss to a minimum. Once a package of nuts has been opened or the shell removed, it is best to refrigerate them immediately in a sealed container. Once the package is opened, transfer the nuts to an airtight container and put them in the refrigerator. Shelled ones hold much better than shelled walnuts, while going to cold storage works best for both varieties.
Nuts should have a fresh nutty scent, but if they seem to smell more like stale oil or cooking oil, the nuts have spoiled. Of course, after those 12 months, you'll find stale nuts here and there, but most of the kernels will be fine. Refreezing frozen and thawed walnuts will greatly diminish their quality, making them soft and tasteless. Because of their high fat content, walnuts do not adapt too well to excessive exposure to harsh environments.
Because there are many ways to store walnuts, it can be difficult to keep track of how long they stay good.