Open the bag and a dry toastiness drifts out. Pour water into the pot and the steam smells a little sweeter. The leaf is the same, yet the word that comes to mind changes each time.
What follows traces the compounds behind the aroma, from the leaf to the steam to the liquid in the cup.
Toasty, sweet and green
Cupped in both hands, the tea sends steam past the nose. No single compound decides the aroma; three words bundle it instead.
Toasty, sweet, green. The research, too, gathers the smells under these three. Of them, the toastiness and the sweetness are what the fire made.
No source names one compound as the lead, and the most that can be said is that the smells fall into three bundles. Next comes what was measured in the leaf, the steam and the liquid.
Dry leaf and rising steam
Bring the nose to the dry leaf and the toastiness reaches far back. Change where it is measured, and the compounds at the top change too.
One method dilutes an aroma step by step and ranks compounds by how far they can still be smelled. In the leaf itself, a toasty compound and a sweet one shared the top step. The steam, and the liquid with the leaf removed, were measured the same way.
In the steam only one compound reached the top, while the liquid held more there. The sources go as far as saying the line-up shifts with the place, even within one tea. The reason lies with water, steam and the nose.