Why Costco Customers Have To Frequently Return This Nut

One of our favorite perks of a Costco membership is exclusive access to its Kirkland Signature range of products. The private-label brand has some pretty impressive names under its belt, but that doesn't mean that every item is a hit. One product that sees frequent returns is the Kirkland Signature Walnut Halves, which several unsatisfied shoppers have reported as rancid.

"I'm not sure if this is a supply chain issue ... but I've had to return this item at least a few times over the past year. And yes — I do refrigerate them the moment I open them," one Redditor complained. "Then I bought some actually fresh, in-shell walnuts... and my god... the difference in taste and smell was night and day." While the nuts hold a very strong 4.8 stars on Costco's website, a little snooping into the one-star reviews revealed that the rancidity issues aren't just isolated to the Reddit thread. Several reviewers also noted that they believed the walnuts have seen a sharp decline in quality in recent years. 

As of 2022, it was California-based Mid Valley Nut Company that supplied Costco's walnuts, which, ironically, was only uncovered as a result of one of Costco's biggest recalls due to reports of the nuts being stale and rancid. We can't say for certain if Mid Valley Nut Company still supplies Costco's walnuts, but since the recall, customers continue to raise concerns about the nuts' quality.

There are a few reliable ways to tell if your Kirkland Signature Walnut Halves have gone rancid. The first clear giveaway is the smell. Expired walnuts often have a sharp, bitter odor, with one Redditor in that same thread describing it as similar to "paint thinner." If you happen to be unfortunate enough to taste one, the difference will be obvious. Fresh walnuts are firm and crunchy with a mild, nutty flavor. Rancid walnuts tend to be soft and rubbery, and leave an unpleasant aftertaste.

Unfortunately, if you've ended up with a bad batch of walnuts, there's not much you can do to salvage them, as all the healthy, fatty oils have already oxidized into unpleasant compounds. On top of that, eating spoiled nuts can increase your chances of foodborne illness. If you'd rather not toss them straight into the trash, you can repurpose them by adding them to your compost pile to enrich your vegetable garden, or even spreading them around plants as a DIY mulch.

To keep your walnuts fresh and extend their shelf life, it's best to freeze them as soon as you get home from the store. Another smart option is to buy walnuts in the shell (nature's built-in packaging), which helps hold off premature oxidation. While cracking each walnut does take a bit more time and effort, the added freshness and longer shelf life can make it well worth it!