Solar-cured tobacco, Bastam, Iran Curing and subsequent growing old allow for the sluggish oxidation and degradation of carotenoids in tobacco leaf. This makes particular compounds from 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/