Every home cook knows that to get that extra dose of flavor, one needs to toast their spices like all the professionals. I’m here to tell you this not only unnecessary it’s counter productive.
The stated reason for this practice is that it release the aromatics makes the spices that much more potent. If you stop to consider this, it’s obvious why this makes no sense. Once the aromatics have been released they will float away and indeed the kitchen smelling amazing is proof that indeed that the aromatic oils are busy floating away, never to be seen or heard from again. If you want your kitchen to smell good, toast your spices. If on the other hand you want your guests to enjoy flavorful food, don’t toast the spices, instead heat your spices together with the food, especially food that has either oil or water which will bond to the flavorful aromatics and be released when the food is being chewed.
One goal of cooking with spices is to move the flavorful compounds from one ingredient to another (ie from the coriander seed to your chicken ). If you simply toast the spices the flavor will move from your pan into the oil that you toasted the spices in and into the kitchen air which while delicious for the cook does nothing for the guest.
Of course you can create delicious infusions by heating spices in oil and then using the oil to coat the food, but even that is better accomplished with a bit more oil and gentle heat. Sure there are certain flavor reactions you can get from toasting, essentially various Maillard reactions, but there are better ways to achieve that on a larger surface area of your food then on the poor spices which make up about 1% of a dish. Someone may point to an obvious counter example like toasted sesame seeds which taste nothing like sesame seeds. This is true, certain seeds completely change the flavor profile after being heated, but even that flavor is better imparted with a bit of toasted sesame oil. So why do chefs keep recommending this technique. The extra step is rather annoying and requires attention/technique – spices burn very quickly – and it makes the surrounding kitchen smell amazing so it must be what it’s imparting that delicious aroma into the food.
Street vendors toast spices as advertising, it’s easy to get customers to be excited about a dish if the cart smells really good, a bit of wasted aromatics into the street air are worth every penny if it draws customers in.