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