Why On Earth Are People Putting Olive Oil in Their Coffee?

TL;DR: Adding olive oil to milk for foaming can both help or inhibit foam creation. It often makes more foam that seems to be made of larger, less stable bubbles, though results depend heavily on the foaming method used. It also introduces a flavor to coffee that not everyone will love. We give this a solid "meh!" at best.

If you're a coffee purist, you may feel personally attacked by most caffeine-related trends of the past few years (espresso martinis! Dalgona! All the other ones!). Then Starbucks introduced Oleato, a line of drinks infused with extra-virgin olive oil that appears to be an attempt to capitalize on a minor trend of steaming milk with olive oil that has become popular among some coffee drinkers (see exhibits A, B, and C showing the interest about this technique over at Reddit).

The claims in favor of adding olive oil to the milk? That it creates a frothed or steamed product that more closely resembles the velvety microfoam skilled baristas are able to make—you know, the microfoam that allows them to pour you pretty little latte hearts instead of fluffy clouds of milky bubbles that just sit atop the coffee like a pompadour. Some people also seem to like the flavor combination.

This got me wondering: Is it worth adding extra fat to the equation when whipping up your milky coffee at home? We did what this site does best—opened up some bottles of EVOO and tried it for ourselves.

How We Tested

I along with Serious Eats' culinary director Daniel Gritzer and associate editorial director Megan O. Steintrager, made test batches in our kitchens with our own supplies and brewing materials, which helped us test the technique across a range of bean styles, brewing methods, and milk-frothing gear.

I brewed three eight-ounce cups of Peet's Coffee (Dark Roast Major Dickason Blend) using a Keurig brewer, and then I frothed one ounce of steaming hot whole milk with one teaspoon of Grazia extra-virgin olive oil for each one using three frothing methods: a handheld electric milk frother; a Nutribullet blender; and shaken in a Mason jar. I didn't add any sugar to the coffees. I also tested the frothing properties of the hot milk on its own (without oil) to provide a comparison.

Daniel pulled shots of Stumptown Hair Bender on a Gaggia Classic espresso machine, then steamed/frothed six ounces of whole milk with one teaspoon olive oil two ways: with the espresso machine's steam wand and using a Nespresso-brand electric milk frother, which heats and whisks the milk at the same time, using the frother's lower-volume whisk (a spinning piece of plastic with two arms). He also prepared separate samples of the whole milk with and without the olive oil in the Nespresso device using the higher-volume metal whisk, which looks more like a classic milk-frothing whisk featuring a circular coil. None of his samples were prepared with sugar.

Megan used an Aerolatte stick frother on 1/4 cup of hot whole milk combined with 1 teaspoon of extra-virgin olive oil and brewed her freshly ground medium roast La Colombe XO XO coffee in an Aeropress.

Each of us looked at how each method impacted the quality of the milk foam and the final coffee in terms of viscosity, foam structure and quality, and, of course, taste.

What We Observed

One of the biggest takeaways from our tests was that there was wide variability on the EVOOed milk's ability to foam depending on the method used. Some methods, including the Nespresso device with the low-volume plastic whisk and the espresso machine steam wand failed to produce almost any quality foam at all, and what it did produce dissipated quickly (Daniel notes that he has not yet mastered the art of making microfoam with the steam wand, but the results with the oil were still far worse than anything he's achieved previously with plain whole milk).

My battery-operated handheld frother created the most EVOO-spiked foam in my tests; it was more frothy and less dense and stable than the non-oiled milk while lasting a similar amount of time. It had a smooth, creamy viscosity similar to something like half-and-half; the olive oil flavor was noticeable but not overpowering.

Daniel's results with the metal-coiled whisk in the Nespresso device were similar to my handheld frother, which makes sense since they work in similar ways: His olive oil–milk was almost fully converted to foam with hardly a trace of liquid milk left (which didn't happen with the plain milk sample), but it was less dense and stable.

On the flip side, my Nutribullet blended milk-and-oil was fast and fleeting and there was a noted bitterness. We know from Daniel's extensive olive oil research that "natural bitter compounds in the oil called phenols are water-soluble, so high-speed blending of oil with any water-based ingredient…can draw them out." In this case, the milk likely pulled the bitter components out of the oil, making the whole drink less palatable.

Megan's assessment was mixed: "The foam was fairly dense and didn't break on top of my coffee, but it tasted terrible both on its own and when added to the coffee. It seemed to just sit on top and provide an unpleasant prelude to each sip."

In even our most successful foamed samples of olive oil–milk, we all noted a yellowish, oleaginous (that's fancy talk for "greasy") texture, and an olive oil flavor that ranged from "tolerable" to "flat-out NO!"

So! Should You Add Olive Oil to Coffee?

I was surprised that my first sips of the olive oil coffee went down smoothly, but my tolerance for it decreased from there. Daniel and Megan were much less enthralled with the flavor impact of olive oil on their coffees. “Why would you do that to coffee?” Megan asked.

We were all surprised by how variable our results were with the olive-oil–spiked milk depending on the foaming method used; it's definitely not a reliable method for guaranteed foam improvement, but in some cases it does seem to help, making more, but lesser quality foam—at an oily price. It's safe to say that adding oil to milk introduces a tricky little variable that seems in some ways to help and in some ways hurt foam creation.

If you do want to try it, we'd say your best bet is a handheld, battery-powered frother or a similar device like the Nespresso; blenders and Mason jars should be avoided, while espresso-machine steam wands may only work if you're already an ace at microfoams.

Final note: I tried adding an extra teaspoon of olive oil to my milk and immediately regretted it. Moderation is key here, and no matter what, your mileage will almost certainly vary.