How to store opened walnuts and hazelnuts

Once opened, walnuts and hazelnuts should be protected from heat, light, air and moisture. A cool, dry cupboard can work for a small amount you plan to use soon. For nuts that will sit for several weeks, a sealed container in the refrigerator or freezer is generally the better option.

Why do walnuts and hazelnuts go rancid?

Nuts contain oils that react with oxygen over time. This process, called oxidation, can produce stale, paint-like or otherwise unpleasant smells and flavours. Rancidity is a quality problem distinct from mould growth. The University of California, Davis, advises refrigerating or freezing nuts that will not be used within a few weeks.

When is pantry storage enough?

Keep short-term supplies in a clean, dry, airtight container, away from direct sunlight, ovens and other heat sources. Resealable packaging may work if it closes securely and protects the contents. Retain the original label so you can check the manufacturer’s storage instructions and best-before date.

Avoid repeatedly topping up an old container with new nuts without cleaning it first.

How should you refrigerate or freeze them?

For longer storage, put the nuts in a well-sealed container in the fridge. Freezing is useful when you buy larger amounts for baking: divide them into portions so you do not repeatedly expose the whole batch to warm, humid air. Let the closed container warm gradually before opening to reduce condensation.

There is no single reliable storage period for every product. Whole or chopped nuts, raw or roasted products, packaging and actual storage temperature all make a difference.

Do chopped and roasted nuts keep as well?

Chopped nuts have more exposed surface than intact kernels and generally lose quality faster under the same conditions. Roasting can also change storage behaviour. UC Davis’s technical storage guidance distinguishes nuts in the shell, whole kernels and pieces, rather than treating them as interchangeable.

When should you throw nuts away?

Discard nuts with a clearly rancid smell or flavour. If you find visible mould, unusual dampness or signs of insects, do not try to rescue them by roasting. Heating is not a dependable way to remove hazards associated with mould.

Check nuts before adding them to cakes, pesto or other dishes. Cold storage slows deterioration; it does not reverse damage that has already occurred.

Shells, whole kernels and chopped nuts

The shell helps protect a nut from its surroundings. Shelled kernels have more direct exposure to air and moisture, while chopped pieces expose even more surface area. This is why it makes sense to chop nuts just before using them.

Roasted and chopped products can behave differently from intact raw nuts. Do not assume that a storage estimate for an unopened package still applies after opening.

Planning ahead for baking

If you buy nuts for holiday baking, separate what you will use soon from the rest. Keep a small working portion in a tightly closed container and store longer-term supplies in sealed portions in the fridge or freezer.

Mark the opening date and keep the original packaging instructions. Avoid repeatedly opening a cold container, and never seal damp nuts for storage.

Rancidity is not the same as mould

Rancidity is mainly a deterioration in fat quality that changes smell and taste. Mould is microbial growth and some species can produce mycotoxins, creating a different concern.

Do not rely on roasting to make mouldy nuts suitable to eat. Discard nuts with visible mould, abnormal moisture or signs of infestation, and throw away those with a distinctly rancid smell.

Frequently asked questions