Sunshine-cured tobacco, Bastam, Iran Curing and subsequent getting older allow to the slow oxidation and degradation of carotenoids in tobacco leaf. This provides specific compounds during the tobacco leaves and gives a sweet hay, tea, rose oil, or fruity aromatic flavor that contributes towards the "smoothness" in the smoke. https://broadfar.com/heated-tobacco-shaping-a-safer-sustainable-smoking-future/