Refrigeration not essential for linseed (flax seed) oil
We are often asked about how linseed oil should be stored. While keeping your oil in the fridge or freezer is the best place to store it, there is a bit of mythology about this and you really don’t need to worry if it is left or even kept out of the fridge – keeping it dark is more important.
Oil is different to milk
We are all used to foods like fish and milk which often will go noticeable bad if allowed to warm up for even a short period. This is because the spoilage of milk, fish and meat is caused by microbes which reproduce exponentially as they warm up so even when you cool the item back down the gazillions of microbes are still in there working away and making it go bad. Oil is very different and it isn’t affected by microbes but oxidizes naturally, like almost every other substance, some oxidize a bit faster than others.
Simple chemistry of oils
A lot of vegetable oils are made of 18 carbon chain fatty acids. These are a series of oils which while they share many physical characteristics and appear superficially similar behave differently as regards stability. Saturated fats like cocoa butter and beef dripping are saturated and very stable; monounsaturated fats as found in olive oil are still relatively stable; the polyunsaturated LA, alpha linoleic fatty acid, found in sunflower, corn, rapeseed and other vegetable oils has two double bonds and is less stable; Linseed (flaxseed oil) which is ALA, alpha linolenic acid, is one step more unsaturated and more unstable (but that’s part of its characteristic that makes it so valuable for our bodies).
Cooler is better but so is convenience
As you can see this is a simple linear series of increasing unsaturation and reduced stability. The later is reflected in its shelf-life. When we produce cold-pressed linseed oil we are producing an oil for health so are more concerned about making sure you get the healthiest product. Just as we don’t refrigerate chocolate or beef dripping, olive oil or even vegetable oils refrigeration is not essential for linseed oil. However refrigeration is the best place to store your oil. The cooler something is the slower chemical reactions like oxidation happen. In the grand scheme of things the difference between the fridge and ambient, (your kitchen cupboard) is only about 15 degrees centigrade and as temperature goes all the way down to -273oC those 15 degrees is not enormously significant, it’s just better and at the end of the recommended use by period it will be fractionally fresher though we have never been able to detect a difference. It’s because cooler is a bit better that coffee roasters recommend you store your fresh coffee in the fridge or freezer; do you though? Most people actually keep their coffee where it’s convenient for use and similarly with their linseed oil. Even so we will still recommend that you keep your oil in the fridge and unused bottles are best stored in the freezer until needed.