Reference point
A stick of Tra Bong cassia with the outer layer lightly scraped.
Do this before you read on. An entry only works when you have just smelled the thing.
Sweet, hot, almost a taste before you have tasted anything. That feeling of heat is not purely smell but a response of the trigeminal nerve — the same system that tells you chilli is hot and mint is cold.
This means that when you smell cassia you are using two senses at once while thinking you use one. Separating the two is the hardest exercise in the spicy family.
It is quite different from the leaf of the same tree. The bark is rich in cinnamaldehyde, so it is sweet and hot; the leaf is rich in eugenol, so it leans heavily towards clove. One tree, two parts, two essential oils that cannot replace each other.
How to smell it
Lightly scrape the outer layer of a stick of Tra Bong cassia to expose the inside, and smell at once. Pay attention to separating two sensations: the smell comes first, the heat about two seconds later. Smell too long and the heat drowns everything and you can no longer tell anything apart.
Why this one is hard
Because the brain merges the smell and the feeling of heat into a single experience. Separating them takes patience and many short sniffs rather than one long one.
Don’t confuse with
This entry
Cassia cinnamon bark
Spicy family
The bark is sweet and hot; the leaf leans heavily towards clove, with almost no sweetness.
Scientific note
The difference between cassia bark and cassia leaf lies in the biosynthetic pathways in the tree. The bark accumulates cinnamaldehyde, the leaf accumulates eugenol, and the same genome gives two different results depending on the tissue. This is called organ specialisation, and it is more common than many people think.
In Vietnamese life
Tra Bong cassia and Yen Bai cassia are the two most famous cassia regions of Vietnam, and both are Cinnamomum cassia, not Ceylon cinnamon. The two species differ considerably in their coumarin content, a point export markets care about more than the domestic market does.