Stalk position effect on harmful and potentially harmful cigarette smoke constituents in Burley tobacco: a case study
Cured leaf chemistry varies sharply according to stalk positions and variations of smoke yields of harmful and potentially harmful constituents (HPHCs) are also expected.
To quantitatively assess the effects on HPHC yields, Burley leaves of the cultivar TN 90LC were produced in a replicated agronomic trial in Bergerac (France), according to standard practices and gathered by stalk position (from bottom to top: lugs, cutters, leaves, tips). The tobaccos were made into cigarettes which were mechanically smoked under the Canadian intense smoking conditions according to WHO's testing proposal. The mainstream smoke (MSS) contents of 32 HPHCs were determined using in-house and recommended methods.
Presenting HPHC yields by mass of burnt tobacco during puffs, and from bottom to top plant position, carbonyls and tobacco specific nitrosamines tended to decrease while some volatile organic compounds (VOCs) (1,3 butadiene, benzene, toluene) and benzo[a]pyrene remained at similar levels. Some VOCs (isoprene, acrylonitrile) and carbon monoxide increased. Nicotine, phenols, hydrogen cyanide, aromatic amines and ammonia increased sharply. In contrast, due to higher nicotine yields in the upper positions, the ratio to the MSS nicotine decreased or stayed constant from bottom to top for all compounds except ammonia.
If the HPHC ratio to nicotine were regulated, this would create a dilemma: increasing the share of upper stalk positions in the Burley part of blends may bring the nicotine level above regulatory and consumer acceptance limits, whereas decreasing it may exceed ceilings for some ratios. If alternatively absolute HPHC yields were regulated, another dilemma would arise, between constituents and stalk positions.
Blending is an expert exercise of selection to find the optimal balance between sensory profiles, regulations and naturally variable raw tobaccos. Regulatory scenarios impact differently on this exercise and clarification from regulators will be needed in order to determine the direction for new tobacco variety developments.