A virgin, cold-pressed oil, made from impeccable raw materials, can lose most of its qualities in just a few weeks. Not because of a manufacturing defect, but simply because it was poorly stored.
Understanding Oxidation
Vegetable oil is composed of fatty acids, some of which have double chemical bonds. It is these double bonds that give oils their nutritional value—they characterize unsaturated fatty acids, the only ones the body cannot produce on its own.
They are also what make them fragile.
Oxygen, light, and heat attack these double bonds and trigger a chain reaction. Peroxides first form, with no perceptible taste or odor. Then these peroxides break down into aldehydes and ketones, which are responsible for rancidity.
Two important consequences.
Firstly, an oil can be largely oxidized long before it smells rancid. By the time the nose detects it, the degradation is already advanced.
Secondly, the richer an oil is in polyunsaturated fatty acids, the more vulnerable it is. The number of double bonds determines its sensitivity. An omega-3 fatty acid like alpha-linolenic acid, with its three double bonds, oxidizes much faster than an omega-9 like oleic acid, which has only one.
The Four Enemies
Light
Ultraviolet radiation triggers photo-oxidation. It is faster than classical oxidation, and it primarily degrades the compounds that we sought to preserve: polyphenols, tocopherols, carotenoids.
An oil exposed to light loses some of its active ingredients long before its expiration date. Transparent glass offers no protection. Tinted glass filters some of it. Dark and opaque glass, or metal, truly protect it.
Heat
Heat accelerates all oxidation reactions. An oil stored next to a stove or above an oven undergoes repeated thermal cycles, each accelerating its degradation.
Oxygen
Each opening introduces air into the bottle. The volume of oxygen in contact with the oil—what is called the bottle headspace—increases as the content decreases.
This is why a large bottle opened for months degrades faster than a small one consumed quickly, under identical storage conditions.
Time
Even perfectly preserved, an oil ages. It never gets better with time. For oils rich in polyunsaturated fats, the optimal consumption window is measured in months.
Refrigerator or Room Temperature
In the Refrigerator: Polyunsaturated-Rich Oils
Flax, camelina, hemp, borage, evening primrose, walnut, pumpkin seed, black seed.
These oils have many double bonds. Cold significantly slows down oxidation reactions. They may thicken slightly, which is not a problem.
Flaxseed oil is the extreme case. Its fragility is such that French regulations require opaque packaging, a maximum volume of 250 ml, nitrogen inerting before sealing, and a shelf life of less than nine months.
At Room Temperature: Monounsaturated-Rich Oils
Olive oil, high-oleic sunflower oil, macadamia oil.
These oils are dominated by oleic acid, which has only one double bond. They are naturally more stable and do not require refrigeration.
The refrigerator is even detrimental to them: olive oil solidifies and crystallizes below a certain temperature. This phenomenon is reversible and does not alter the product, but it makes daily use impractical.
A closed cupboard, away from any heat source, is sufficient.
And Blends
A blend combining oils with different profiles should be stored according to its most fragile component.
A blend containing flax, borage, or evening primrose goes in the refrigerator, even if other oils in the formula would not require it.
Never Heat Polyunsaturated-Rich Oil
Oils rich in omega-3 and omega-6 degrade with heat and produce undesirable compounds. They should be consumed exclusively raw, added at the end of preparation, on an already served dish.
For cooking, oils rich in omega-9—olive, high-oleic sunflower—are much more stable. However, they still lose some of their phenolic compounds and vitamin E.
Important Practices
Close immediately after each use. Oxygen is the main agent of degradation.
Avoid pouring above a hot pan. Steam rises into the neck of the bottle and introduces moisture, which promotes hydrolysis and thus free acidity.
Never pour oil taken out back into the original bottle.
Note the opening date on the label.
How We Addressed These Constraints
These principles are not usage recommendations that we provide after the fact. They determined our packaging choices from the outset.
Opaque Bottles
We discarded transparent glass, and even slightly tinted glass.
The opaque container is more expensive and complicates filling and labeling. It offers no marketing advantage—it even prevents seeing the color of the oil.
This is precisely what makes it a coherent choice: it only serves to protect the product.
A 250 ml Format
A small format is counter-intuitive from a commercial perspective. It increases the unit cost of the container, reduces the basket value, and gives the impression of offering less.
But a large format opened for three months is an oil that slowly degrades in its own bottle as the air volume increases.
250 ml corresponds to about 1 month's consumption at 10 ml per day. This is the format that allows a bottle to be finished while it is still at its best.
Refrigerated Storage
Our blends contain fragile oils. Refrigeration is not an excessive precaution: it is the condition for what was preserved during extraction to remain so until the last spoonful.
This requires a slight change in habit. We prefer to embrace it rather than formulate oils stable enough to remain on a countertop, which would mean removing precisely what makes them useful.