The new oil is in the cellar: what decides whether it will still be good in March

The hard work is done: the olives were picked at the right moment and milled quickly. What comes out of the mill now is the best that harvest could give.

From here on nothing improves any more. You can only keep what is there, or lose it — and the first weeks are when it is lost fastest, because the oil is still cloudy and alive.

The three enemies, in order of damage

They are always the same three, and they work together: light, oxygen, heat.

Light triggers the oxidation of the fats; oxygen feeds it; heat speeds up everything else. Above 20 °C the ageing reactions run, and the first things to go are the aromas and the polyphenols — exactly what sets an extra virgin apart from any other oil, and what we were chasing when we chose the right moment to harvest.

Racking: this is where most mistakes happen

Oil straight from the mill carries water and very fine residues of pulp. In time they settle to the bottom: that is the lees.

Left there, they do not stay quiet: they ferment, and the defect they give the oil above them has a precise name in sensory analysis, “muddy-sediment”. It is the most common way of ruining a good oil without noticing, because it happens slowly.

The practical rule is simple: about a month after milling you rack the oil, leaving the deposit on the bottom of the first container. If the oil is still very hazy you can rack again a few weeks later. Rack slowly, without letting the oil gurgle: every bit of turbulence is oxygen going in.

The container: being full counts as much as the material

Food-grade stainless steel, dark glass and the classic tin are all fine. Plastic is not, for long storage, and neither is clear glass left in the light.

But the material is only half of it. The other half is that the container has to be full: the air left above the oil is oxygen in contact with it, twenty-four hours a day. A fifty-litre drum filled halfway keeps oil worse than two twenty-five-litre ones filled to the cap.

For the same reason it is worth decanting into small bottles or tins what you are going to use, and leaving the rest closed: you open one container at a time.

Where to keep it, in practice

The right range is 14-18 °C, in the dark and away from swings. In a normal house that means a cellar or an internal storeroom, not the garage (cold in winter, hot in summer) and least of all the kitchen: the spot next to the hob is the worst of all, and that is almost always where the bottle in use ends up.

Below 10-12 °C the oil starts to go cloudy and form flakes: it is not a defect and it clears on its own at room temperature, but constant hot-cold swings do harm. A slightly higher but stable temperature is better than one that moves every day.

How long it really lasts

The law requires a best-before date, usually eighteen months. In practice a quality oil, well kept, holds its aromas and bitterness for 12-18 months; after that it is still edible but it is another oil, flatter.

Badly kept, that same oil can lose its best part in a few months. That is why it is worth spending half a day now sorting out containers and racking: in March, when somebody else's new oil is already tired, yours will still be the one from November.

In short

• Light, oxygen and heat work together; above 20 °C they run.
• Rack after about a month, leaving the lees on the bottom. Slowly, without gurgling.
• Stainless steel, dark glass or tin. Never plastic for the long term.
• Full containers: the air above the oil is the damage you do not see.
• 14-18 °C, dark, stable. Never next to the hob.
• 12-18 months of full life if everything else was done properly.

One thing we always say, and it applies here too: storage protects a good oil, it does not save an oil that was born wrong. What makes the difference happened earlier — a tree pruned properly, olives picked at the right point and taken to the mill quickly. The rest is custody.