The difference between Ceylon and Cassia
There are different varieties of cinnamon. The best-known varieties are Cassia and Ceylon. Ceylon cinnamon is aromatic, sweet, sunny, woody and slightly bitter. Ground and dissolved in hot water, it becomes a bit slimy and sticky. Compared to Ceylon cinnamon, Cassia is slightly darker, sweeter, perfumed, penetrating and has a sharper bitter aftertaste. It's got a little hard feel in the mouth.
Cassia varieties from Vietnam and China contain most coumarin, the natural flavouring substance of cinnamon. Ceylon cinnamon contains 1.5-3.0% essential oil, while Cassia contains only 0.5-2% essential oil. This means that the Cassia has slightly less taste.