Sun-cured tobacco, Bastam, Iran Curing and subsequent getting old enable for the gradual oxidation and degradation of carotenoids in tobacco leaf. This makes specified compounds in the tobacco leaves and provides a sweet hay, tea, rose oil, or fruity aromatic taste that contributes on the "smoothness" from the smoke. https://broadfar.com/non-combusted-cigarettes-a-safer-alternative-or-just-a-myth/