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After many delightful meals at a friends home, made by "frying a turkey in an infrared fryer" I decided to get one for myself, specifically the "Big Easy" from CharBroil. Empirically I can see that this 'works' (and quite well) but I'm not sure I understand "How" it works. You have an outer heating space and an inner cooking chamber. Ok, so this heats the food, but what is not clear to me is:

  • How is this "Infrared" (a spectrum of light below 'red')?
  • For that matter, how does it qualify as "frying", to my eyes it looks more like baking .
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    More like roasting. (One style of) Peking duck is done in a very similar way: direct heat radiation. Traditionally against flame but in this case, electric heating. Infrared is just light whose frequency is a little lower that we human beings can not see. Property wise it's almost identical to visible light. – user3528438 Dec 26 '17 at 16:59
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Infrared refers to the region of the electromagnetic spectrum comprised by wavelengths of about 1 and 100 microns. As you said it lies just aside the reddish part of the visible spectrum (called visible based on our vision) and usually revealed by sensors based on semiconductors.

https://en.m.wikipedia.org/wiki/Electromagnetic_spectrum

This invisibility is due to the fact that the energy carried by IR radiation comes in photons or quanta (think of them as small packets or specks of energy which gets involved in absorption / emissions / and other phenomena as indivisible entities) whose size does not fit with the electronic transitions responsible for what we call colours.

Their energy is less and correspond to molecular vibrations and rotations.

Temperature is - microscopically - the motion of particles. The energy carried by IR get absorbed by the food molecular vibrations and rotations and by concomitant collisions get transformed in linear motion too. I.e. the molecules move faster (this happens independently of the way heat is given).The final result is a higher T so that reactions and processes can happen).

The main difference with respect of other cooking is that it works, in principle, even in vacuum. No medium is needed to transfer heat (note that this applies to microwave cooking as well). No convection, conduction but just radiation.

As with microwave oven, the cooking is rather smooth and homogeneous all within the food.

As pointed out in the above comment, this cooking is more a sort of roasting or grilling from above. Note that these two types of cooking are basically IR based.

Every body (in physics sense) emits radiation by virtue of its temperature. All the time that cooking substantially involves a big luminous object, there is IR radiation at work (electrical grill from above, barbecue, roasting via a flame, ...).

Differences and peculiarities of each are due to the concomitance of more than one heating mechanism, like thermal conduction by metallic part, warm air, steam, etc. as well as the presence of a second component (water or oil are not merely media but can be absorbed and/or contribute to taste).

Indeed, from a mechanicistical point of view, the most apart from IR cooking are boiling and frying , which I would say are almost totally based on thermal conduction (convection carries heat to the whole body of fluid then the food is heated by contact).

Still, I do not doubt that your IR fried food resemble that fried in fats. Likely it is moderately crispy all over, more healthy, just a bit less tasty.

(Additional note. Visible and shorter wavelength radiations (x rays) do carry energy, too. Even more, each photon has a high energy than a IR one. It is just that they are primarily involved in higher energy processes at first. They heat up a body after some sort of decay processes that again result in an overall faster motion of particles).

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    How is the heating smooth and homogenous within the food? It seems the radiation would only penetrate a short distance and have to conduct in from there. Do you mean that the heating is even across the surface, with no hot spots? – Sobachatina Dec 29 '17 at 13:03
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    @Sobachatina. Good point. Right that from every radiatively heated point conduction takes place, too. At least if a temperature gradient is there. I will add "rather" before "smooth and homogeneous" that was meant in comparison to cooking in oil or on a surface. However IR radiation has quite a big penetration depth in organic materials. That is why some (para)medical heating device (those in sauna and beauty center) are IR elements rather than radiator. Heat goes smooth and deep in to the muscles with no burning of the sjkin. MW is even more penetrating. It depends however on composition – Alchimista Dec 29 '17 at 13:19
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    @Sobachatima. More on the core: heating on a hot surface is due to collision between the atoms of the pan and the molecules of the food. In IR and MW the energy is in the electromagnetic field, so the latter can propagate through and exponentially decay with deep. Heat is how this energy finally manifest itself. Vis light get reflected - and in part absorbed within mm of our body. IR radiation is mostly absorbed and penetrates to cm extent. Look at white light trough your finger. You will see your nail is red. – Alchimista Dec 29 '17 at 13:26
  • Interesting. Thank you for the explanation. – Sobachatina Dec 29 '17 at 13:37

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