Solar-cured tobacco, Bastam, Iran Curing and subsequent getting older let to the gradual oxidation and degradation of carotenoids in tobacco leaf. This creates certain compounds within the tobacco leaves and gives 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/