Sunlight-cured tobacco, Bastam, Iran Curing and subsequent aging allow for for that sluggish oxidation and degradation of carotenoids in tobacco leaf. This produces particular compounds during the tobacco leaves and gives 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/