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I'm deep-frying croquettes rolled in egg then in breadcrumbs.

Last time I did this I did it in vegetable oil, and had no problems and nothing unexpected happened.

This time I didn't have quite enough vegetable oil, so I topped it up with extra virgin olive oil. Maybe the oil is 80% vegetable oil 20% EVOO by volume.

As soon as I started frying the first batch, I started having huge problems with foam; the oil was foaming up all over the place and even spilled out. Very annoying.

Why might this have happened this time but not last time?

3 Answers3

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Oils foam when they are nearing their smoke point and start to break down. This can happen when you reuse oil a lot, but it can also happen when you are reaching the natural smoke point of the oil.

Vegetable oil is usually a blended oil so the exact smoke point will largely depend on what it was specifically made of, but in general, it will be between 400-450°F. EVOO, on the other hand, has a much lower smoke point of between 350-410°F (depending on quality and filtration level), which is butting up against the temperatures used for a lot of deep fat frying. Even if you aren't reaching the actual smoke point, getting close can be enough to start the degradation process of the EVOO components.

So the likely culprit of your foaming issues is overused vegetable oil, the EVOO getting too hot, or both.

Abion47
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Just try not to heat the oil that much if you are using EVOO. Also, as they told you 'low quality' EVOO depends on what you mean, but for general porpouse, smoke point:

  • AOVEE => 160ºC / 320F
  • VOO => 215ºC / 419F
  • Refined Olive OIL => 240ºC / 464F
  • Olive Pomace Oil => 230-240ºC / 464F

My recommendation definitly is not to heat that much the oil. Your croquettes will also great. Just lower heat and more time to fry it. If this is not an option I recommend Olive Pomace Oil for generic frying (basically because it is cheaper than EVOO and it is not refined, but VOO it is also great option).

Finally I want to comment that there are recipes that are not thought for frying on EVOO instead are thought for frying on Vegetable oil (specifically Sunflower Oil). This is not the case for croquette where I should use Olive Oil, this case it is more more fish frying. Spanish person advice

Ismael
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Extra virgin olive oil, has a lower smoke point compared to many vegetable oils. When you mix it with vegetable oil and heat it, the resulting mixture might reach the smoke point more quickly. This can cause excessive foaming and bubbling, as olive oil has impurities and compounds that can break down and release gases at lower temperatures. Additionally, olive oil’s higher acidity and natural components can contribute to increased foaming. If you want to avoid this issue, consider using oils with a higher smoke point for frying or keep a closer eye on the temperature.

Shubham Sahu
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