Descriptions of roasted stem tea nearly always reach for aroma words: toasty, clean, floral, sweet. Turn the packet over and the ingredients field says only tea. The front is full of scent words; the back needs one.
This piece looks at why stems and a light roast go together, through the compounds behind the aroma.
Why stop early
Break the seal and, behind the toastiness of the dry stems, there is a hint of something floral. To keep that scent, the roast is best stopped early.
The source of the floral scent sits in the leaf bound to sugars. The heat of roasting releases it, and as the roast goes on its share falls.
Neither finding comes from a trial that roasted stems alone. The sources show that stopping early helps the floral scent stay. Whether stems have a scent of their own comes next.
No scent found only in stems
Smell stem tea and leaf tea side by side and the impression differs a good deal. Yet no aroma compound found only in stems has turned up.
When aroma compounds were drawn from a shop-bought stem tea and a sencha, every compound that could be named was the same in both. The report says no compound thought to be peculiar to stem tea was detected. What differed was the balance, with more of the floral compounds in the stem tea.
The samples were one shop-bought product of each. The sources show that the difference lies in amounts, not in kinds. The amounts after roasting are in a different report.