How to Choose and Store Quality Olive Oil at Home

Olive oil quality depends on how the olives were grown and pressed, and on how the oil is handled afterward — from the shelf at the store to the cupboard at home. The International Olive Council (IOC), the UC Davis Olive Center and the North American Olive Oil Association (NAOOA) each publish guidance on grading, buying and storing olive oil, and their recommendations largely agree.

Understand the grade on the label

The IOC defines olive oil grades by free acidity and sensory quality. Extra virgin olive oil must have free acidity, expressed as oleic acid, of no more than 0.8 grams per 100 grams and pass a taste panel with no sensory defects. Virgin olive oil allows up to 2 grams per 100 grams acidity. Lampante virgin olive oil, with acidity above 3.3 grams per 100 grams, is not fit for consumption and must be refined first. Refined olive oil has acidity capped at 0.3 grams per 100 grams, while the blended product simply labelled "olive oil" (a mix of refined and virgin oils) is capped at 1 gram per 100 grams, according to the IOC.

What to look for when buying

1. Check for a harvest date rather than only a 'best by' date. The UC Davis Olive Center advises buying the most recent harvest available; California and European oils are typically harvested October to December, Southern Hemisphere oils May to July, and oil is best used within about 15–18 months of harvest.
2. Prefer dark glass, metal tins or bag-in-box packaging. Clear glass or plastic lets in light, which degrades the oil faster, according to the UC Davis Olive Center.
3. Look for third-party quality seals, such as those from the California Olive Oil Council, where UC Davis notes standards are stricter than the USDA minimum.
4. Check where the oil was actually produced, not just where it was bottled, since packaging location can differ from the origin of the olives, per UC Davis.
5. If you can taste or smell it before buying, expect fresh extra virgin oil to show fruitiness, bitterness and pungency; stale-nut or 'Play-Doh'-like odors signal rancidity, UC Davis says.
6. Buy a size you can finish within a few months. UC Davis recommends buying quantities that will be used up within weeks to a few months of opening rather than large bulk bottles.

How to store it once it's home

The NAOOA summarizes storage advice with the acronym HOLA — avoid heat, oxygen, light and age. The group advises keeping bottles away from the stove, oven or windows, always closing the cap or seal after use, and using fluorescent-light-free, dark locations such as a cupboard or pantry. The IOC likewise states oil should be kept away from excessive heat, air, humidity and, above all, light.

• Store in a cool, dark cupboard or pantry, not next to the stove or in direct light.
• Keep the cap, seal or pour-spout cover closed between uses to limit air exposure.
• Use opened extra virgin olive oil within a few months, according to the NAOOA; UC Davis similarly says oil tastes best within a couple of months of opening, even though it may still be fine for up to two years unopened.

Shelf life: unopened vs. opened

Sources differ slightly on numbers but agree on the overall pattern: oil degrades faster once air reaches it. The NAOOA states olive oil generally remains viable for no more than two years from the bottling date and recommends using an opened bottle within a few months. UC Davis notes that oil bought within a year of harvest can keep up to two years unopened, but tastes best used within roughly a couple of months of opening and within 15–18 months of the original harvest date.