There is a half-used bag of walnuts left over from last year’s holiday baking, and you can’t remember when you opened it. Do walnuts go bad? They do, mostly through rancidity and sometimes mold. Here is what UC, the California Walnut Board, USDA and FDA say about shelf life, storage and spoilage signs.
Do walnuts go bad?
The Short Answer : Yes. UC’s consumer nut guide lists walnuts, in the shell or shelled, at about 1 year in the refrigerator and 2 years or more in the freezer. It says nuts keep quality for only a few months at room temperature. The California Walnut Board says walnuts go rancid when they sit in warm temperatures for long periods, and that the best place to keep them is the refrigerator or freezer. Sources vary on the exact times, so treat them as quality estimates, not a promise of safety. Throw out walnuts with visible mold, because USDA lists nuts among foods to discard when moldy. Rancid nuts are poor quality, and we’d toss them too. A normal look and smell can’t rule out harmful bacteria, per UC.
For a complete pantry and fridge reference, see our Food Storage Guide. For related nuts, see whether almonds go bad, whether pecans go bad, whether pecans need to be refrigerated and whether pistachios go bad.
Walnuts: At a Glance
Pantry (room temperature)
A few months for nuts in general (UC). Kansas State lists 4 months for unopened in-shell nuts and 2 weeks once a package is opened
Refrigerator (40°F or colder)
About 1 year in UC’s table. Michigan State lists up to 3 months, and NDSU lists 4 to 6 months for opened nuts
Freezer (0°F or colder)
2 years or more in UC’s table. Michigan State lists up to 1 year
In shell vs shelled
Same refrigerator and freezer times in UC’s table
Moldy walnuts
Discard them. USDA lists nuts under “Discard”
Rancid walnuts
UC says rancid nuts are not unsafe, but quality is poor. The California Walnut Board says to throw them away
“Best by” date
A quality date, not a safety date, per USDA
Best storage
Cold, sealed, and away from strong-smelling foods
Key Takeaways
UC’s consumer nut guide (ANR Publication 8406, August 2010) lists walnuts, in-shell or shelled, at 1 year in the refrigerator and 2 years or more in the freezer. It says nuts keep quality for only a few months at room temperature.
The California Walnut Board says walnuts go rancid when exposed to warm temperatures for long periods. It says to keep them in the refrigerator, or in the freezer if you’ll store them for a month or longer.
The California Walnut Board says fresh walnuts smell mildly nutty, and that walnuts that smell like paint thinner are rancid and should be thrown away. UC says rancid nuts are not unsafe.
USDA’s mold page lists peanut butter, legumes and nuts under “Discard” when moldy, and says not to sniff a moldy item.
UC says refrigeration and freezing do not destroy Salmonella, and that harmful bacteria cannot be determined by sight, smell, taste or texture.
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