The Bitter Truth About Olive Oil

by | Mar 18, 2009
Olive Oil and Balsamic Vinegar

Olive Oil and Balsamic Vinegar

Have you ever had homemade hummus turn out bitter? Have you whipped up your own batch of mayonnaise and found an unpleasant aftertaste? Or are you just confused about why I warned against putting olive oil in a blender for my harissa recipe?

The culprit behind these bizarre phenomena is extra-virgin olive oil, which is very sensitive to mechanical agitation. Upon one reader’s request, I set out to explain the unusual behavior of this common ingredient.

But getting to the bottom of this problem was not easy. The internet is teeming with false assumptions and unfounded hypotheses about why olive oil can become bitter when blended. Most people point their finger at the quality of the oil itself, accusing the chef of using a cheap brand that was bitter before they included it in their recipe. I knew this wasn’t true because it has happened to me several times, and I always use excellent olive oil.

Another common hypothesis is that “heat” caused by the friction of high-speed spinning blades makes the “delicate oils” in the olive oil turn bitter. This explanation makes even less sense, because as most of you know olive oil can be heated in a pan to several hundred degrees and does not burn or turn bitter. There is no way the oil gets hot enough to go rancid after a few seconds in a blender.

The only logical and (mostly) scientific explanation I found for the bitter olive oil phenomenon was from Cook’s Illustrated. I am inclined to trust this source because they essentially run their kitchen like a laboratory, which gives them major credibility points in my book. Also, their reason offers a plausible, mechanical explanation that does not depend upon the quality of the oil itself. I have not seen the data with my own eyes, however, and they do not cite their sources.

According to Cook’s Illustrated, extra-virgin olive oil is the only kind of oil susceptible to becoming bitter. Even pure olive oil can handle blending better than the extra-virgin kind. The reason is because extra-virgin olive oil contains a high percentage of molecular compounds called polyphenols (thought to be cancer-fighters), which are normally coated in fatty acids. Under standard conditions, the fatty acids in the oil prevent polyphenols from dispersing in an aqueous environment. This is because oil and water do not mix.

When these fat molecules are broken into droplets in an emulsion, however, the polyphenols are distributed into the solution and their bitter taste can become apparent. When the emulsion is only lightly blended, the bitterness is not perceptible. But a blender or food processor breaks the droplets down into smaller sizes, increasing polyphenol dispersal. These suspended polyphenols can ruin an otherwise delicious recipe.

The easiest way to avoid this problem is to use either pure olive oil or a different kind of oil altogether, such as canola or safflower oil. Alternatively, if you would like to keep the rich taste of extra-virgin olive oil you can hand whisk your emulsion rather than using a blender. Just be careful not to over work the mixture. You can also start your recipe by blending a small amount of stable oil (e.g. canola), then hand whisking your extra-virgin olive oil in at the end.

Have you ever had problems blending extra-virgin olive oil?

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33 Responses to “The Bitter Truth About Olive Oil”

  1. doug says:

    I just realized a few days ago that the olive oil I’ve been using the last year (infused with peppers) is actually sunflower oil.

  2. Erica says:

    Interesting. I have not tried to use EVOO in anything that required blending or emulsion. I recently have come across a no-soy mayo recipe from Mary Enig’s book/website Eat Fat Lost Fat and am tempted to try it (since I have not had mayo in years now!), but will have to reconsider using extra-virgin olive oil. Thanks for the tip!

  3. Katie says:

    Wow, great picture darya!! (I think I love every single one of them) And thanks for the informative post. I would have just as soon believed you without understanding, but I guess I love to know the “whys” too. Thanks!

  4. Scott says:

    Because of the versitility, tastiness, and health benefits I declare that Olive Oil is a superfood. Anyone agree/disagree?

  5. Travis Saunders, MSc says:

    I always wondered why that happened! Great post.

  6. Darya Pino says:


    Sounds delicious ;)


    Glad I could help. It’s really, really bad to mess up. Ruins everything. Let us know how your experiment goes!


    What would I do without your encouragement? Thanks!


    LOL, you know how I feel about superfoods.


    Me too! Luckily it is not that hard to avoid.

  7. Shannon (The Daily Balance) says:

    I LOVE your blog — so informative!

  8. Michelle says:

    No i’ve never noticed a problem but I trust Cook’s. Good info!

  9. Yod says:

    I think this happens more often than we think. We were just served an olive oil at Buca di Beppo (hardly a temple of cuisine) that was so bitter it tasted like it had been sitting in a rusty can. Now, the oil wasn’t in a recipe, but you have to wonder if the blending process for it was a bit too rough!

  10. Karin says:

    I’m just suprised more people aren’t in an uprage about all the sub-par olive oil that goes around…..I wonder if there is a difference in the lipid profile of high vs low quality olive oil….my guess is yes. And yes I agree Scott, it is definately a superfood.

  11. Anonymous says:

    Love the pic, Darya. Is your olive oil really that green? Mine is always an orangy color.

  12. Chris Clarke says:

    The bitterness is a feature, not a bug! F’rinstance: McEvoy’s Olio Nuovo, which you can get in season at the Ferry Building, is polyphenolicious.

    • Lindell says:

      My current olive oil is deeply green, cold pressed extra virgin. It has a wonderful deep fruity aroma. When I tried to make a quick mayo tonight it went extremely bitter (i would normally use sunflower oil or something for this, but didn’t have any). I then tasted the oil as is, and found it to have an overly bitter after taste….not nice. Though I used it in a dressing the other night and it wasn’t detectable??? I’m very concerned about rancid oils and I can smell them a mile away. This one doesn’t smell rancid. Any ideas??

  13. fas says:

    To be honest, I have always heard people say Olive Oil rules, guess everything does not come all good.

  14. As soon as I saw the caption of Foodgawker, I knew I had to hop over here to find an explanation for one of my problems! I’ve blended EVOO in the blender before with no problems (like in a couple of salad dressings I make) but every single time I try to pulse my chimichurri in the food processor it gets SO nasty! I started googling stuff to find that EVOO could be the culprit, but never once did anyone say it was the actual *blending* that caused it, the explanation always pointed toward low quality EVOO or something. But I tried it with every brand out there and still no luck. I only put it in the blender because I like a super fine texture, but I guess I’ll have to attempt to get that with a knife. Good post- thanks!

  15. Funny, when I make chimichurri, for some reason it always tastes better if I chop everything by hand rather than use a food processor. Not sure why. As far as the olive oil, good info, I’ll have to keep this in mind,

  16. Allison says:

    Great olive oil post. I haven’t noticed that it gets bitter, but I have noticed that when you put it in the food processor it loses some of it’s flavor. I always use a mortar and pestle to make things like pesto or anything with an expensive olive oil – for this and other reasons. What brand of olive oil do you like best? I’m big on Sicilian oils, but after my recent move to Berkeley, I’d really like to find a quality local one.

    • Darya Pino says:

      I like Stonehouse, but I’m a big fan of fruity oil. McEvoy is great if you like a little more bite. You can find both at the Ferry Building. You should come to the farmers market tomorow!

  17. Hi Darya

    Great post, photos and explanation! I never knew that extra virgin olive oil could be so sensitive when mixed with other ingredients. I and my husband produce our own 100% extra virgin, hand-picked olive oil “Ginestre 12″ from the Abruzzo region in Italy. We have 61 young olive trees and we are relative newcomers to olive oil production.

    Nothing beats the flavour of virgin olive oil and I use it every day in all my cooking.

  18. Elisheva says:

    fantastic post! i’m new to your blog and becoming a big fan fast! thanks!

  19. julie says:

    I’m really glad I found this post! I have chickpeas soaking right now to make hummous for a party tomorrow, and I always use EVOO. I may use a bit of grapeseed to help it through food processer, than add the olive oil after it’s all done. I’ve never noticed the bitterness per se, but have always been surprised by how much salt I needed to add to make it taste okay.

  20. Karen B. says:

    Never put olive oil IN Hummus. You make the hummus (just garlic, garbonzos, tahini, water for consistency), spread it on a plate and drizzle the olive oil over the top. Put on a few olives cured in oil for saltiness and voila.

  21. Karen B. says:

    Forgot the lemon. :-)

  22. Sasha says:

    Thank you for writing this detailed explanation. I recently had a very disappointing homemade aioli experience because of this reason. It emulsified very well and was quite beautiful, but it was so bitter that I had to discard it right away :(

  23. Rob says:

    I’m very happy you wrote this post for the first time my chimichurri came out bitter. I used a little too much vigin olive oil after reading this article I pressed the exess oil out and it tasted much better.. So I took the rest of the oil out and replaced it with unblended virgin olive oil and let it sit. What did I get? Perfect chimichurri..

    Thank you

  24. Miss Bee says:

    Very strong, high quality EVOO is bitter. It is a desirable quality. The olives are picked early, on the under-ripe side so to give it that bite. The bitterness is a direct result from the high level of anti-oxidants in the green fruit. To say it’s a problem is to be under-informed.

    If you want the generous health benefits from the Mediterranean Diet and EVOO, you should always seek out the bitter stuff. Fact.

    If you don’t want it IN your hummus, drizzle it on top after you’ve made it… even better.

  25. Marta says:

    Thank you I’ve been breaking my head thinking what I was doing wrong with my ( otherwise ) delicious Mayo.I tought I had ( over and over ) dropped some lemon seeds on the mix LOL
    I’ll try with another oil.

  26. Michelle Kemp says:

    Great informatn thanks.. ive just made mayo with extra virgin oil in the blender and it’s terribly bitter! Back to canola oil for me….

  27. kostly says:

    I have just made mayonnaise for the first time, and it looks great, but tastes terrible! I didn’t use a blender, just whipped it up by hand with a wooden spoon. I must be machine-like in my efficiency! I used extra virgin olive oil as it was all I had in the cupboard. Is there any way of saving the mayo once it has gone down this bitter nasty route, or is it all over?

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