Sunshine-cured tobacco, Bastam, Iran Curing and subsequent aging allow for for your sluggish oxidation and degradation of carotenoids in tobacco leaf. This makes certain compounds from the tobacco leaves and provides a sweet hay, tea, rose oil, or fruity aromatic taste that contributes towards the "smoothness" in the smoke. https://broadfar.com/heated-tobacco-shaping-a-safer-sustainable-smoking-future/