Solar-cured tobacco, Bastam, Iran Curing and subsequent getting older allow to the gradual oxidation and degradation of carotenoids in tobacco leaf. This creates certain compounds during 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/