Sun-cured tobacco, Bastam, Iran Curing and subsequent aging allow for to the slow oxidation and degradation of carotenoids in tobacco leaf. This provides particular compounds during the tobacco leaves and gives a sweet hay, tea, rose oil, or fruity aromatic flavor that contributes on the "smoothness" on the smoke. https://broadfar.com/oraco-global-trends-in-heat-not-burn-products/