Non-hydrogenated peanut oil becomes hydrogenated when heated?

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Discussion Overview

The discussion centers around the claim that non-hydrogenated peanut oil may become hydrogenated when heated, particularly during frying. Participants explore the chemical processes involved, including oxidation and the potential effects of temperature and water on the oil's composition.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • Some participants question whether peanut oil can become hydrogenated without the presence of hydrogen, suggesting that oxidation of double bonds is more likely to occur when heated.
  • There is speculation about whether hydrogen naturally present in peanut oil could separate at high temperatures, but this is met with skepticism.
  • One participant introduces the idea that rapid temperature changes and the introduction of water during frying might contribute to changes in the oil, though the legitimacy of this claim is uncertain.
  • Another participant discusses the theoretical energy requirements for hydrogen production from water and questions whether typical frying temperatures are sufficient for such processes.
  • Concerns are raised about the health implications of these chemical changes, particularly regarding rancidity and the formation of unhealthy compounds.
  • A participant mentions that the industrial process of hydrogenation involves high temperatures and catalysts, which differs from home cooking methods.
  • It is noted that many store-bought peanut butters contain hydrogenated oils to prevent separation, suggesting that cooking temperatures may be less of a concern for consumers.

Areas of Agreement / Disagreement

Participants express differing views on the processes that occur when heating peanut oil, with no consensus reached on whether hydrogenation occurs or the implications of heating the oil.

Contextual Notes

The discussion includes various assumptions about chemical reactions, the role of temperature and water, and the nature of peanut oil, which may not be fully resolved or clarified.

Flatliner
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Can't find a reliable source on the internet for the answer to this question. Some claim that heating peanut oil at high enough temps to fry food causes the oil to become partially hydrogenated therefore causing it to become an "unhealthy" oil. Is this true?
 
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That's just a guess on my side, but I don't see how it can become hydrogenated when there is no hydrogen. However, with plenty of atmospheric oxygen around, oxidation of the double bonds (no matter what the exact products are) seems quite possible.
 
Borek said:
That's just a guess on my side, but I don't see how it can become hydrogenated when there is no hydrogen.
Is there hydrogen already naturally in peanut oil that separates from molecules at high temps and hydrogenates the oil?


However, with plenty of atmospheric oxygen around, oxidation of the double bonds (no matter what the exact products are) seems quite possible.
That's unhealthy?
 
Flatliner said:
Is there hydrogen already naturally in peanut oil that separates from molecules at high temps and hydrogenates the oil?

No, there is a hydrogen, but it doesn't separate.

That's unhealthy?

Yes, that's more or less how fats get rancid.
 
The claim I've heard isn't that heating it to high temperatures does it, but the rapid temperature drop along with introduction of water and then reheating when you drop whatever frozen food you're frying into it. I'm also not sure if this is a legitimate claim or an internet myth, but perhaps with those additional details, Borek will have more insight if it's possible.
 
The way Moonbear heard it seems more reasonable, since theoretically: [tex]E + 2H_2 O = 2H_2 + O_2[/tex]

where E is energy.

But then there's at least two important questions to ask:
1) how much Energy is required; does a fryer produce it?
2) how much water is required to produce enough hydrogen to saturate the food (in a dilution of peanut oil?) to a significant level?
 
Hi Moonie :smile:

Pythagorean said:
The way Moonbear heard it seems more reasonable, since theoretically: [tex]E + 2H_2 O = 2H_2 + O_2[/tex]

where E is energy.

But then there's at least two important questions to ask:
1) how much Energy is required; does a fryer produce it?

No way, thermal decomposition of water requires insane temperatures - over 2000 deg C for a single digit percent decomposition.

On the other hand, water doesn't have to decompose first, such thing could be a several step process, yielding a similar final result. But I find it highly unlikely.

2) how much water is required to produce enough hydrogen to saturate the food (in a dilution of peanut oil?) to a significant level?

This is the simplest part. Assuming oil is a trigliceryde with three monounsaturated fatty acids, each 18 carbons long, its molar mass is 879 g/mol. There are three double bonds, so in theory it can react with up to three moles of water. In other words - you would need 56 g of water to fully saturate 879 g of oil. That's not exact, as oil is not just a single trigliceryde, but IMHO it is a quite good estimate

I can be wrong, but I don't like this explanation. Water can be added to the double bond, that's a well known reaction, but it doesn't yield alkane and oxygen - it yields secondary alcohol. Besides, water has much better place to attack - it can hydrolise the ester, yielding glycerin and fatty acid itself. The latter reaction is catalyzed by bases and acids, so it won't be very fast in the fryer, but seems much more likely to me.
 
I am now hungry for beer battered halibut
 
The partial or complete hydrogenation of unsaturated vegetable oils is an industrial process called "sparging". It involves treating the oil under high temperature and pressure in the presence of a catalyst such as powered nickle together with molecular hydrogen.

http://www.tutorvista.com/science/vegetable-oil-saturated
 
Last edited:
  • #10
most store-bought peanut butter already has hydrogenated oil added so that it doesn't separate. natural peanut butter will separate with a layer of light oil on top if you leave it out, meaning you've either got to stir it with a butter knife regularly or leave it in the fridge.

so, for most of us, worrying about cooking temps is a bit like trying to shut the barn door after the horse has escaped.
 

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