Whole Flaxseed
In ideal conditions, whole flaxseed can last for several years and may still remain viable enough to germinate. Brown seeds are generally tougher than golden seeds and can often be stored for longer.
For flaxseed to store well, it must be thoroughly dried. Flaxseed sold in shops is usually dried sufficiently. However, if moisture content is around 8% or higher, seeds may attract the storage mite Tyrophagus putrescentiae.
Mites are tiny arachnids, related to spiders, but much smaller — typically less than 1 mm. In warm, damp conditions they reproduce rapidly and can quickly spoil a bag of flaxseed. Even in a dry kitchen cupboard, flaxseed can occasionally become infested.
The fridge is a good place to store flaxseed, as mites reproduce very slowly at low temperatures. For long-term storage, the freezer is undoubtedly best. Mites cannot reproduce below 0 °C. Whole flaxseed will keep reliably for at least two years when frozen.
For shorter-term storage, the fridge is also suitable.
Ground Flaxseed
In addition to the risk of mites, grinding breaks the protective outer shell (husk) of the seed and exposes the oil-rich interior to oxygen, which can lead to rancidity.
Ground flaxseed should be stored in a cool, dry place. Whether you bought it pre-ground or ground it yourself, it is best kept in the fridge during its best-before period. Unopened bags are ideally stored in the freezer, which can help extend freshness by a couple of months.
Flaxseed Oil
Flaxseed oil is more sensitive to light than to temperature. Therefore, the most important aspect of storage is protecting it from light. Dark, UV-protective glass bottles are ideal.
Cold-pressed flaxseed oil is naturally variable. Shelf life can depend on the seed variety, growing conditions, soil, climate, storage conditions, and pressing temperature. Some oils retain their sweet, mild taste longer, but generally, the shelf life for maximum freshness is about six months.
Storing flaxseed oil in the freezer can help preserve freshness for a few extra months.
Store flaxseed oil in a dark, cool cupboard — ideally in the fridge.
Typical shelf life: ~6 months
When stored in the freezer:
Typical shelf life: ~8 months from fresh