This Is the Real Reason Olive Oil Often Comes in a Green Bottle

Cruise the condiment aisle at your local grocery store and you'll notice a sea of green bottles: olive oil, in plastic and glass containers and from budget picks to upscale options. But why the monochrome? Dark green bottles are near synonymous with olive oil, and the answer involves a lot more than aesthetics. Here's what's behind that signature bottle shade, according to olive oil sommeliers and chefs.

Why does olive oil come in green bottles? Light is one of olive oil's main enemies and can cause it to go rancid, says olive oil sommelier Emily Lycopolus , author of The Olive Oil & Vinegar Lover's Cookbook. Storing olive oil in a dark green bottle helps filter out ultraviolet rays that can cause oxidation.

"Like putting sunglasses on, the dark green protects the oil from the light," explains Emilie Berner , chef/instructor of plant-based culinary arts at the Institute of Culinary Education 's Los Angeles campus.

Light can also impact the flavor of the olive oil, interfering with its fruity taste, says Paul DiBari , chef-instructor of culinary arts at the Institute of Culinary Education 's New York City campus.

But there's more to consider than just flavor. Rancid olive oil contains free radicals, which are linked to cancer when found in high concentrations in the body, Lycopolus points out. Olive oil stored in darker bottles might also offer more health benefits. Even in a well-sealed bottle, oxidation can occur when olive oil is exposed to light alone because of its naturally-occurring chlorophyll, which converts light into oxygen. "The process of oxidation us[es] up antioxidants, so many of the healthful qualities are no longer present in a rancid or oxidized oil," Lycopolus says.

Does an olive oil bottle have to be green? A green bottle isn't an indicator of better quality than other tinted glass or opaque containers.

Olive oil sommelier Susan Abranovic, founder of Susan Julia Olive Oil , explains that dark green bottles were commonly thought to offer the best protection. But, "over time, with much testing, what is understood today as ideal is a dark glass bottle."

Still, many olive oil bottles remain green.

"Green glass is easier to find, widely produced, and offers good UV protection," Lycopolus says. "It also doesn't require harder-to-find ingredients like cobalt, which is used to make blue glass. The majority of manufacturers create green and amber glass, so it's readily available."

However, any dark-tinted glass or opaque container made of ceramic or stainless steel is a great option. "They block all light and are non-reactive, unlike other metals [like iron and copper] that can oxidize and then be found in the olive oil," Lycopolus says. "Olive oil is a sponge and soaks up whatever it's in contact with."

When selecting olive oil, avoid plastic bottles, which are more porous than glass, ceramic, or stainless steel options and which can let in too much light. Some studies have also shown that plastic packaging can transfer microplastics to olive oil, Abranovic says.

How to store olive oil Olive oil is essentially fruit juice, Abranovic says. "It should really be placed in the produce section, because olive[s] [are] a stone fruit."

Olive oil starts to oxidize as soon as it's harvested, Lycopolus adds. But storing olive oil in a cool, dry place like your pantry can help prevent oxidation.

"Once olive oil is bottled, it has a shelf life of 18–24 months. And some olive oils even less," DiBari says. Because the oil starts to break down quickly once it's been unsealed, "you should use it within six months of opening."

Lycopolus thinks you should try to finish your bottle even faster: It's best to enjoy your olive oil within six weeks if you're able "as the open air and oxygen in the bottle will encourage it to go rancid faster."

How to pick out a good olive oil Olive oil sommeliers and chefs have a few recommendations for selecting a quality olive oil.

Choose a product packaged in dark glass, stainless steel, or ceramic bottles or tins.

Look for a harvest date on the bottle to give you an indication of how fresh it is. "The fresher the oil, the better," Lycopolus says. "It is more healthful and flavorful."

Find a bottle with a cultivar or varietal. "There are well over 1500 cultivars of olives, each with their own unique flavor profile," Lycopolus says. "Ideally, you'll want to know what is in your bottle and not a 'blend of oils from the EU,' which doesn't tell you much about the contents, flavor, or freshness.

Look for any identification of chemistry analysis. "Something like 'FFA < 0.3' will let you know that the oil has had some testing done to show quality, authenticity, and stability," Lycopolus says. (FFA stands for Free Fatty Acid.)

Pick a bottle stored in a cool spot. "You don't want it to be on a top shelf, exposed to lights, near a window, or near heat," Abranovic says.