Toasting many spices,and heating some peppers increases and brings out the spice and heat. Other foods, such as onions, shallots and garlic (yes, I know they're from the same family; just can't think of other examples right offhand), it mellows their bite.

Is there something scientific to this? It doesn't seem to be component specific, as capsaicin is the main heat element in peppers, but some, such as jalapenos, actually seem to mellow a bit with roasting. Unless the ones I've roasted were just randomly mellower like jalapenos from even the same plant can vary anyway?

I understand the pepper itself doesn't actually get hotter; cooking just releases some of the capsaicin oils. But why would it affect other foods the opposite way, and how would peppers even vary in how they respond to cooking heat?

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    Regarding onions and garlic: AFAIR they contain allicin (a sulfur-containing organic compound) which is their main hot agent, but it decomposes during heating and after being left out on air, which is why onions are a lot less hot if you fine chop them and leave them for 20 minutes. Onion grown in sulfur-less soils is not hot. Sep 28, 2012 at 9:17
  • You're kind of mixing two questions here. One is why capsaicin is different from other things, and the other is why your roasted jalapenos didn't seem to get hotter.
    – Cascabel
    Sep 28, 2012 at 14:48
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    @jefromi: Thanks for the input. The mellowing effect on jalapenos seems to be each time I've tried them roasted or fried or otherwise heated; it wasn't a random failed dish. The confusion was that while both jalapenos and other peppers contain capsaicin, cooking heat seemed in my experiences to mellow the jalapenos but increase the heat in several other types of pepper. Same as it mellows the bite in coffee beans (roasted being much less bitter than raw), and alliums, but brings it out in spices. Sep 29, 2012 at 20:15
  • bitter and spice/heat are two different things though. You would have to consider the pH of the food, the starting % of capsaicin, age of the peppers, level of heat applied, % of cells that were denatured, etc. Plus for things like onions/garlic, the "hot" agent is typically found all throughout the food, whereas, the peppers tend to have their capsaicin concentrated in the ribs and seeds.
    – Brendan
    Dec 5, 2012 at 20:01

1 Answer 1


I expect that you have already considered the most probable answer. For some spices, the aromatic compounds are released by some heat, but are not destroyed. Thus their effect is heightened. For other compounds, even a small amount of heat will destroy them and thus reduce their effect - see Mischa's comment.

I believe that the difference essentially lies in at what temperature a flavoursome compound starts to degrade.

  • Thanks, that does make sense. I know all I'd listed were in the same family, but the mellowing also applies to coffee beans. Sep 29, 2012 at 20:11

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