I threw out three bags of walnuts last year before I figured out what was happening. They’d taste fine when I bought them, then a month later they’d bite back with that weird paint-like aftertaste. I assumed I was buying bad nuts. Nope. I was storing them wrong.

Nuts go rancid because of heat, light, and oxygen. The oils in nuts — especially walnuts, pecans, and pine nuts — oxidize fast at room temperature. Once that happens, there is no fixing them. But preventing it is almost too easy.

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Freezer Is Best, Fridge Is Fine

Nuts last up to two years in the freezer and about a year in the fridge. I portion mine into small freezer bags, squeeze the air out, and toss them in the freezer door. They do not freeze solid — you can scoop out a handful and they are ready to use immediately.

Roasted nuts go rancid faster than raw ones because heat has already started breaking down the oils. Buy raw nuts and roast what you need when you need it. Your nuts will last longer and taste better.

Glass Over Plastic

After my freezer-bag system started feeling wasteful, I switched to small glass jars. Glass blocks light better than plastic containers and does not absorb odors. I use leftover jam jars with tight lids. The nuts stay fresh and I can see exactly how much I have left.

One thing I learned the embarrassing way: label the jars. Chopped walnuts and chopped pecans look identical after a month in the freezer. I put pecans in my banana bread thinking they were walnuts and spent the whole loaf trying to figure out why it tasted wrong.

Smell Before You Use

Rancid nuts will not make you sick in small amounts — but they taste terrible and the oxidized oils are not great for you either. If a nut smells like paint, old oil, or crayons, toss it. Trust your nose. Fresh nuts smell sweet and nutty. Rancid nuts smell like the back of a craft supply closet.