Warning: I am a cooking noob. I might overlook something ridiculously simple.

Anyway, I just made my first pesto sauce (do you call this a sauce?). Basil, Parmesan cheese, garlic, etc. At the end, I added vegetable oil. All was good and I was proud. Put it on bread and on pasta, and it was very tasty.

However, I stored what I had left in a small jar in the fridge. Only one day later, and it became solid! You can clearly see that the oil had solidified. Why is this? In fact, I poured in too much oil and took some out, and what I took out I put it in the fridge, in a cup (just the oil). This is also one massive block. I am used to oil solidifying, but AFTER you use it to cook. The oil that I used has not been cooked, and the rest of the oil I bought at the store is stored in a cupboard, in its original packaging, and is still liquid.

What went wrong?

Extra question:

  • Can I somehow still de-solidify this and still eat this?
  • 1
    Weird... I never had this problem. What type of oil did you use? Pesto is usually made with extra-virgin olive oil.
    – nico
    Mar 31, 2012 at 20:48
  • It was a vegetable oil, not sure what kind, but not olive oil. I'll try olive oil next time... Apr 1, 2012 at 0:51

2 Answers 2


Most pestos use olive oil, which solidifies at around 6 degrees celsius - just over the temperature of the average fridge. The shop-bought pestos you buy probably adulterate the olive oil with other kinds of oils.

In any case, you'll be able to eat your pesto just by leaving it out at room temperature for a few hours, or by just scooping it out and adding to your hot pasta.

  • I don't think adulterate is the right verb to use, unless you want to imply a mislabeling of the product
    – nico
    Apr 1, 2012 at 16:39

It most likely solidified due to the presence of the parmesan cheese - essentially a fat as opposed to an oil. You are right in thinking the latter doesn't solidify in the fridge on its own.

If you leave it out for a few hours it may melt, but you are probably better off simply melting it in a saucepan and using to dress pasta.

  • 2
    I find olive oil does often solidify in the fridge, in my experience, including without the presence of other fats.
    – jcorcoran
    Mar 31, 2012 at 22:46
  • Thanks for the reply. But as I mentioned in the post, I initially poured too much oil in the pesto, and took away some of it. This I put in a cup (just the oil), and I put it in the fridge. This also solidified! And that was just the oil, not mixed with Parmesan. That would mean this is not at fault. Or would the fact that it was mixed briefly with Parmesan have caused this? And if Parmesan is at fault, why does 'industrial' pesto not solidify? (sorry for all the questions!) Apr 1, 2012 at 0:54
  • 1
    @user16441 You should never have to apologize for asking too many question. We encourage it :) However, if you do have additional related questions, you will probably have better luck getting an answer to it by editing your original post and adding that. A lot less people will probably ending up reading all the comments compared to the body of a question. Btw I am specifically referring the "why doesn't industrial pesto solidify" question you added in the comment. It's related enough to add to your original question.
    – Jay
    Apr 1, 2012 at 2:34
  • Try just putting some plain oil in the fridge, it'll solidify too. The commercial pesto probably is using a different oil (e.g., canola)
    – derobert
    Apr 1, 2012 at 4:42
  • 1
    It would be pretty crappy pesto to not use olive oil. But I imagine they put in some kind of anti solidifying agent. Apr 1, 2012 at 11:49

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