Sunshine-cured tobacco, Bastam, Iran Curing and subsequent getting older allow to the gradual oxidation and degradation of carotenoids in tobacco leaf. This generates specific compounds in the tobacco leaves and offers a sweet hay, tea, rose oil, or fruity aromatic taste that contributes for the "smoothness" of the smoke. https://broadfar.com/oraco-global-trends-in-heat-not-burn-products/