Sunlight-cured tobacco, Bastam, Iran Curing and subsequent getting old let for the sluggish oxidation and degradation of carotenoids in tobacco leaf. This makes specific compounds inside the tobacco leaves and provides a sweet hay, tea, rose oil, or fruity aromatic flavor that contributes for the "smoothness" in the smoke. https://broadfar.com/oraco-global-trends-in-heat-not-burn-products/