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This answer talks about the amount of heat required for cooking fried rice which tastes similar to restaurants.

I want to understand the science behind it. Please explain.

Community
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Aquarius_Girl
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    I've edited to make this specifically about fried rice, which is what that answer was talking about. Amount of heat certainly affects other things too, but it's a pretty broad question without at least having a specific example to start from. (I've also changed "fire" back to "heat" since that answer never mentioned fire - though it may be relevant as well, as Escoce points out.) – Cascabel Jan 28 '16 at 17:25

3 Answers3

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It's an issue of thermodynamics.

When you're cooking food, the food cools itself off through evaporative cooling and the energy being used to cause chemical changes in the food (eg, caramelizing sugars).

If you have too much food in the pan, the balance is overwhelmed by evaporative cooling, and thus you can only get to the boiling point of water.

To change the equation, you need to do one of the following:

  1. Use a more powerful heat source.
  2. Cook less food at a time
  3. Reduce the amount of moisture in the food before cooking it.

You'll often see advice for #3 -- such as patting dry steak or chicken before grilling it, as without it, you won't get good browning.

You can't do that when you're dealing with sauces. You can try cooking less, but with sauces you cause more problems -- if the pan size is the same, the area for evaporation is the same, so you don't really improve the balance.

With a sufficiently sized burner, you can actually heat sauces above the boiling point, as you're putting in energy faster than evaporation can cool it. This which will change the chemical reactions that occur, thus the resulting chemical compounds and the resulting flavor of the food.

Joe
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Basically there's a specific chinese style of cooking that requires extremely large amounts of heat to get a specific mix of textures and flavours. By keeping the amount of heat high and constant, food is cooked quickly, and with a certain sort of flavour - referred to somewhat poetically as "wok hei"

Its fairly specific to chinese cooking, and something more likely to be found eating out, unless you have the right kind of high heat stove with roaring flames coming out like a rocket motor.

Journeyman Geek
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It's not just the amount of heat. The heat component IS really important, but that funny taste that you only get from chinese takeout fried rice, really has to do with the fire.

The smoke from the fire, even completely combusted fire envelopes the wok and the food within it, the food in that wok is absorbing the smoke and that's what imparts that Chinese takeout wok flavor. It's most noticeable in fried rice because fried rice is delicately flavored which allows you to taste it almost directly as a prominent feature/flavor of the dish. This is what is called Wok Hei and it only happens when you use fire.

Escoce
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  • Surely there's far more smoke from the food and oil smoking inside the wok than from the gas burner itself. Gas burns *really* cleanly, so even if there is a really subtle aroma from it (I've never noticed it, but could be!) it'd surely be covered up by the much stronger aroma from the smoke in the wok. Am I missing something? – Cascabel Jan 28 '16 at 17:26
  • Doesn't matter, and that's why I specifically said even completely combusted fire, there is still some incombustible residue left, including carbon dioxide which contrary to intuition has a flavor. – Escoce Jan 28 '16 at 17:30
  • Just to iterate this. It only happens when using open flame. If heat were the issue, then why can't it be duplicated with non-flame heat sources? – Escoce Jan 28 '16 at 17:33
  • I don't actually know how well you can do without a flame - that's an assertion that wasn't made in the answer the OP linked. But assuming you can't do well without it... non-flame heat sources don't heat the side of a wok, only the bottom. So they'll be transferring large amounts of heat into less of the food, and causing less caramelizing and burning and smoking inside the wok. – Cascabel Jan 28 '16 at 17:36
  • Yes it is. To quote: "To impart wok hei the traditional way, the food is cooked in a seasoned wok over a high flame while being stirred and tossed quickly." And no, as you mention at the top of your comment, you cannot do this without flame. – Escoce Jan 28 '16 at 17:43
  • It would be good if you could provide sources for your claims in your answer. – Aquarius_Girl Jan 28 '16 at 17:47
  • I did, I quoted the link in the other persons answer. – Escoce Jan 28 '16 at 17:48
  • Okay, so you need a flame. Awesome. And regardless, high flames improve the flavor, agreed. But as I've pointed out, there's a great explanation for why that doesn't involve natural gas combustion flavor. I'm not disagreeing that there may be such a flavor, but I'd like to see some support for the claim that a subtle burned natural gas flavor coming in from outside the wok makes a meaningful contribution when there's a much, much stronger (and much more abundant) flavor from burned rice and oil inside the pan right there with the food. – Cascabel Jan 28 '16 at 17:50
  • @Escoce The part you quoted makes no mention of natural gas burning creating flavor. In fact, the rest of the passage supports the idea that the flavor is not actually from natural gas burning: "it additionally allows for the splattering of fine oil particles to catch the flame into the wok" (there's cooking oil burning) "It should also be noted that cooking with coated woks (e.g. non-stick) will not give the distinct taste of wok hei." (the stuff burning in the pan matters) and... – Cascabel Jan 28 '16 at 17:53
  • ..."the flavour imparted by chemical compounds results from caramelization, Maillard reactions, and the partial combustion of oil that come from charring and searing of the food at very high heat in excess of 200 °C" (no mention of flavor from gas burning) – Cascabel Jan 28 '16 at 17:53
  • Wow, the fried rice I get from takeout isn't burned. Not even a little bit. Fine call what i am saying original works. Yep that's right, I am the guy who figured it out. Lol. On a serious note, I know this site is all about giving the best answer, but sometimes the best answer isn't quoted or paraphrased from elsewhere. I like being here to ask questions and give the best answers I have, but this isn't a paid gig, sometimes the reader needs to take it on themselves to do a little research on their own. Maybe once in a while and original work makes its way here too. – Escoce Jan 28 '16 at 17:55
  • @Escoce Indeed, the rice itself isn't burning, but very small amounts of stuff in the pan is, and that imparts flavor. I'm sorry if I made it sound like I meant the bulk of the food you consume was actually burned. – Cascabel Jan 28 '16 at 17:57
  • This isn't simple mailliard reaction, it's a taste that is unique to wok cooking over flame. Go ahead and make some rice bread and tell me the crust tastes the same as that funky wok fried rice taste. Explain that one to me? – Escoce Jan 28 '16 at 17:57
  • Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/34979/discussion-between-jefromi-and-escoce). – Cascabel Jan 28 '16 at 17:58
  • Honestly it really isn't that important to me. I have reached that point where I am shutting down and not interested in _being right_. – Escoce Jan 28 '16 at 18:00