Toasting spices - not always helpful??
I make batches of chili powder from dried chiles, cumin seed, sometimes coriander berries. I've been toasting all of the whole components by heating them in a hot dry skillet before grinding.
But if the point of toasting is to release more flavor compounds, and I'm storing the majority of my batch in a plastic tub, am I wasting my time? Especially if I'm not using the chili powder that day.
Can this enhancement really last? And in the case of the chiles, weren't they already heated once in the drying process?
And finally, what is superior about the dry heat from toasting that is impossible to get from the inevitable water/fat mediated heating of your ingredients in your actual dish?
I'm somewhat skeptical of the 'release' idea. The molecules that I smell during toasting are not going stay around to flavor the stew. Once I smell them they are gone.
Still I recognize that the freshly toasted cumin gives a raita a different taste than untoasted. I use this as an example where the cumin is the star. But I haven't compared freshly toasted with previously toasted.
There is no grounds for skepticism here. Toasted spices are different from raw spices--not necessarily superior (though I think it's fair to say that some spices (e.g., coriander, cumin, szechuan peppercorns, mustard seeds) are superior toasted).
As for what is "superior" about dry heat, wet heat is limited to the boiling point of water (212 F). Dry heat can go much higher.
Generally, you should only toast as much as you plan to use soon.
I typically roast and then grind quite a few varieties of spices, then store. I do think you lose flavor by grinding and storing for long periods of time. But I don't have time to roast, allow to cool to room temperature, and grind on a frequent basis. The loss of flavor isn't so devastating as to render your spices useless. But there is a loss.