A dark glass bottle of olive oil in a cool cupboard beside a clear bottle left in sunlight on a windowsill, the two shown side by side, with a small cup of oil and a spoon

Does Olive Oil Go Bad? Yes, and Here Is How to Tell, How to Store It, and How Long It Really Lasts

Olive oil is fruit juice. It is pressed from a fruit, it is at its best in the weeks after pressing, and it declines from that day on, which is a fact the olive oil trade has spent a century helping shoppers forget. It does not spoil in the way milk spoils; an old bottle will not make you sick. But it goes rancid, and rancid oil has lost the aroma, the bitterness, the peppery finish and most of the polyphenols that were the reason to buy extra virgin instead of a jug of something refined. Most home kitchens are cooking with oil that has already crossed that line, because it was old when it was bought and then kept by the stove in a clear bottle. This page answers the questions people search, in order.

How long does olive oil last?

Unopened, a well-made extra virgin oil in a dark bottle or tin, stored cool and dark, is at its best for twelve to eighteen months after the harvest and acceptable for up to two years. The number that matters is the harvest date, not the best-by date, which producers set at eighteen to twenty-four months from bottling and which tells you nothing about when the olives were picked. Opened, the clock speeds up. Once air is in the bottle, oxidation begins in earnest, and an opened bottle stored well is good for about three months, and noticeably faded by six. Stored badly, by the stove in a clear bottle, it can be tired in a month.

Where the opened bottle lives Useful life after opening Why
On the counter beside the stove, clear bottle Four to six weeks Heat from cooking, light through the glass, and air every time it is opened: all three oxidizers at once
On the counter away from heat, dark bottle Two to three months Light is blocked; room temperature still works on it
In a cupboard, dark bottle or tin, cap tight Three to four months Cool, dark, and closed: the conditions the oil was bottled for
In the refrigerator Four to six months, at a cost Slows oxidation further, but the oil clouds and thickens and must warm before use; fine for a large tin you decant from

How to tell if olive oil has gone bad

Smell it, then taste a spoonful, per the tasting method. Fresh oil smells of something: grass, artichoke, tomato leaf, apple, almond, butter. Rancid oil smells of old nuts, crayons, putty, stale walnuts or, at the far end, nothing at all, and it tastes flat, waxy and slightly greasy with an unpleasant finish that lingers. There is no cough at the back of the throat, because the polyphenols that caused it are gone. A second sign, before the smell: an oil that used to be green-gold and cloudy going pale and perfectly clear, or a musty, wine-like or vinegar-like edge, which means the olives fermented before milling and the oil was never good. Once you have smelled rancid oil knowingly, you will recognize it in most restaurants and in the bottle you grew up with.

Should you refrigerate olive oil?

You can, and for a large tin you decant from it is sensible, since the cold slows oxidation and the tin protects from light. The oil will cloud and may solidify, which is harmless and reverses at room temperature, though the texture and the aroma are duller cold and a bottle taken in and out of the refrigerator daily suffers from the condensation. For a working bottle you use every day, a cool cupboard is better: it is nearly as protective and the oil is ready when you are. Never store oil in the freezer, and never above or beside the stove, which is where most people keep it and the worst place in the house.

What does the harvest date mean, and why is it the only date that matters?

Olives in the northern hemisphere are harvested from October to January, and the oil is at its peak in the months right after. A bottle labeled with a harvest date lets you count from the pressing; a bottle labeled only with a best-by date could contain oil pressed twenty months before you read it, and it often does. Look for "harvest" or "raccolta" or "cosecha" and a month and year on the back label. If it is not there, assume the worst, and buy from producers who print it; our buying guide lists what else to read on a label, and our mill piece explains why oil is freshest in the season it is made. In September, the best bottle on any shelf is from the previous November; in December, the new harvest is arriving and last year's should be discounted.

Why does it go bad? The three enemies

Light. Ultraviolet light drives oxidation directly, which is why serious oil is sold in dark glass or tins and why a clear bottle on a windowsill is a slow way to ruin it. Heat. Every ten degrees Celsius roughly doubles the rate of the reactions that turn fresh fat rancid, and the shelf above a stove sits well above room temperature for hours a day. Air. Oxygen is the reagent; a half-empty bottle has a large surface of oil exposed to it, which is why a big bottle that takes a year to finish goes off before the last quarter is poured. Buy the size you will use in two or three months, and keep the cap on.

Is old olive oil unsafe?

No, in the ordinary sense. Rancid oil is unpleasant rather than dangerous at the levels found in a home kitchen; the oxidation products are ones nutrition science regards as worth avoiding, but the practical reason to discard it is that it tastes bad and has lost the compounds that made it worth buying. If it smells of putty, do not cook with it; the smell survives heat and flavors the dish.

What to do with a bottle past its best

An oil that is faded but not yet rancid is fine for high-heat cooking where its aroma would have been lost anyway: roasting, sautéing, frying. Move it to the stove and open a fresh bottle for finishing. An oil that is properly rancid is finished as food; it can season a wooden board, lubricate a hinge, or go into the compost with the cooking fat. Do not pour it down the drain.

The rules, in one paragraph

Buy by harvest date, within a year of it, in dark glass or a tin, in a size you will finish in three months. Keep it in a cupboard, cap tight, away from the stove. Open one bottle at a time. Taste it when you open it so you know what it should be, and again if it has been open a while. Use the good one raw and the tired one for the pan. The oils on our shelf carry harvest dates and are at 263 Josephine Street in Cherry Creek, Denver, and ship nationwide from theambrosianpantry.com. Denver's dry air and strong light are hard on an open bottle, which the storage guide covers along with everything else in the cupboard.

Sources & Further Reading

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