Solar-cured tobacco, Bastam, Iran Curing and subsequent growing older make it possible for for the sluggish oxidation and degradation of carotenoids in tobacco leaf. This makes particular compounds during the tobacco leaves and gives a sweet hay, tea, rose oil, or fruity aromatic flavor that contributes into the "smoothness" https://broadfar.com/non-combusted-cigarettes-a-safer-alternative-or-just-a-myth/