US Patent 6895974 Tobacco processing

Tobaccos are cured in a manner so as to provide tobaccos having extremely low tobacco specific nitrosamine (TSNA) contents. Harvested Virginia tobacco is subjected to flue-curing so as to provide flue-cured tobacco. During the curing processing steps, contact of the tobacco with nitric oxide gases, such as those produced as combustion products of propane burning heating units, is avoided. Tobacco in curing barns is not subjected to direct-fire curing techniques, but rather, heat for tobacco curing can be provided by heat exchange or electrical heating methods.