Put dry leaf over a low flame and for a while nothing happens. Then, quite suddenly, the room smells different. The green note pulls back and a toasted one rises. It is not the smell that came out of the packet.
What follows looks in turn at the makings of that toastiness, what is formed, what is lost, and how the aromas change places with temperature.
The toastiness was in the leaf
Each turn of the wooden spatula makes the toasted smell a little deeper. Its makings were inside the leaf all along.
The compounds that carried umami and sweetness turn into other things under heat. Nothing has been added from outside. The sources can say where the materials come from, and that is all. What heat forms out of them is the next part of the story.
A crowd of new aromas
Lean close to freshly roasted leaf and the aroma arrives in many layers at once. Roasted tea holds more than eighty compounds that were not in the leaf before.
A family of compounds formed when sugars and amino acids join under heat makes up most of the aroma. New compounds were also born from the source of umami together with sugars. The temperatures and times used in the research are tabled in the chapter that checks roasting temperatures.
The research names what was formed and stops there. Behind the new aromas, some things are being lost.