How to Store Cold-Pressed Oils So They Don't Go Rancid

Wood-pressed oils are made to keep their natural colour, aroma and flavour, and that is exactly why they ask a little more of you in the cupboard. Because they are unrefined, they hold on to the reactive natural compounds that refining strips away, which means they oxidise faster than refined oils. The good news: keeping them fresh is mostly about three habits, and none of them cost anything.

The three enemies of unrefined oil

Rancidity is oxidation. Three things drive it, and all three are easy to design out of your kitchen:

• Light, sunlight and bright kitchen light speed up the reaction.
• Heat, warmth from the stove, the oven or a sunny windowsill accelerates spoilage.
• Air (oxygen), every time the bottle is open, oxygen gets to work.

Refined oils have had those reactive natural compounds removed, so they shrug off light, heat and air for longer. An unrefined, wood-pressed oil keeps those compounds on purpose, that is part of what you are buying, so it oxidises faster and deserves a slightly more careful home.

Simple storage habits that work

You do not need special equipment. A cool, dark spot and a well-sealed bottle do most of the work:

• Store cool and dark, a cupboard away from the stove and oven, never on the counter beside the hob or on a sunny sill.
• Keep the bottle tightly sealed between uses so oxygen cannot creep in.
• Prefer opaque or dark containers that keep light off the oil.
• Avoid leaving a large headspace of air above the oil; decanting into a smaller bottle as you use it up helps.
• Wipe the rim and reseal after pouring, so old oil and air do not collect at the neck.
• Buy sizes you will actually use in a few months rather than one large bottle that sits open for a year.

Notes for each oil

Coconut oil

Wood-pressed coconut oil solidifies below roughly 24°C, turning cloudy or firm and white. This is completely normal, it is the oil reacting to temperature, not a sign of spoilage. Warm it gently to liquefy it again; standing the bottle in warm water or in a warmer corner of the kitchen is enough. There is no need to refrigerate it.

Groundnut (peanut) oil

Treat groundnut oil like the others: cool, dark, sealed, finished within a few months.

Sesame oil

Unopened and stored cool and dark, sesame oil keeps for many months, check the best-before date on your bottle. Refrigeration slows oxidation, which can help if you use it slowly, though chilling may cloud or thicken the oil. That clouding is reversible and is not spoilage: let it come back to room temperature and it clears.

How to tell an oil has turned

Your nose is the best tool you have. An oil that has gone rancid develops a harsh, "painty" smell and a bitter taste. If you notice either, discard it, a turned oil will not improve, and it spoils the dish.

As a technical freshness benchmark, the FSSAI permits cold-pressed and virgin oils a peroxide value of up to 15 milliequivalents of active oxygen per kilogram (meq O₂/kg). Peroxide value is one of the standard measures of how far oxidation has progressed; lower is fresher.

Sources

• Refined vs unrefined coconut oil, Healthline: https://www.healthline.com/nutrition/refined-vs-unrefined-coconut-oil
• Edible-oil standards (peroxide value limit), FSSAI, Food Products Standards, Chapter 2.2: Fats, Oils & Fat Emulsions: fssai.gov.in (PDF)

Want help choosing which oil suits how you cook? Read our guide on how to choose a cooking oil, or see our range of wood-pressed cold-pressed oils.