Sun-cured tobacco, Bastam, Iran Curing and subsequent getting older allow with the slow oxidation and degradation of carotenoids in tobacco leaf. This generates particular compounds inside the tobacco leaves and gives a sweet hay, tea, rose oil, or fruity aromatic taste that contributes on the "smoothness" in the smoke. https://broadfar.com/heated-tobacco-shaping-a-safer-sustainable-smoking-future/