CORESTA Sub-Group TSNA in Air-Cured and Fired-Cured Tobacco
CORESTA Sub-Group TSNA in Air-Cured and Fire-Cured Tobacco
(Established as TSNA Task Force in 2002)
Chair: Colin Fisher, University of Kentucky, USA
- Create survey of critical farmer practices
Subcommittee Chair: George Scott, Universal Leaf
Objective 1 status: completed
Survey submitted to Scientific Commission
- Conduct collaborative study to investigate standard deviation of moisture content of marketing packages
Objective 2 status: dropped
Initial moisture content of marketing package not as important as storage environment of marketing package.
- Develop standardized nornicotine screening protocol so that baseline levels of nornicotine are comparable in tobacco seed varieties used by investigators
Subcommittee Chair: Anne Jack, University of Kentucky
Objective 3 status: completed
Agreed that Univ. of KY screening protocol could be used without adding "LC" to variety name, provided that acknowledge was made that this protocol was used. If "LC" is added to name, Univ. of KY protocol must be used.
Current Objectives (objectives revised January 2015):
Objective 1) Determine proper placement of data loggers in curing barns to best represent the true curing conditions in the barn.
Subcommittee Chair: vacant
Objective 1 status: 2 studies completed
Cooperative study conducted in 2008 and 2009 by Virginia Tech and University of Tennessee (coordinated by Danny Peek, Virginia Tech). Study directly compared the influence of growing and curing environments and compared environmental data from HOBO meters placed on tier rails between tobacco and within tobacco during air-curing of burley. Results of experiment indicated that growing environment Iin addition to curing environment) also impacts TSNA formation. Results also suggested that at low temperatures during curing, relative humidity has lesser influence on TSNA. Results also showed that when evaluating TSNA across many environments, there is too much variability to confirm that higher relative humidity and higher temperature always results in higher TSNA.
Collaborative experiment did not directly compare placement of metering equipment. However, it is the opinion of the TSNA subgroup that:
- At least 1 meter should be placed in the top and bottom tiers of barn
- When tobacco is not all housed in the barn at the same time, meters should be placed in tobacco at each time of housing
- Meters should be placed within the tobacco, hung from the center of stick at same level on plant where sample will be collected
- Meters should be calibrated each year ideally to ensure accuracy (particularly RH)
An additional experiment relevant to Objective 1 has been conducted at two locations in Kentucky in 2012 and 2013 to evaluate correlation between air-curing environment at various locations within barns and corresponding TSNA.
Final Study Grant Report (approved by Scientific Commission June 2015)
Objective 2) Review issues of post-cured storage and ventilation parameters.
Subcommittee Chair: Lowell Bush, University of Kentucky
Objective 2 status: Review and report completed
Shi, H. et al. 2013. Changes in TSNA content during tobacco storage and the effect of temperature and nitrate level on TSNA formation. J. Agric. Food Chem. 61:11588-11594.
Objective 3) Sampling
- 3a: Define proper sampling method of post-cure tobacco for TSNA determination
- 3b: Determine optimal method for sample preparation for TSNA determination
Objective 2 status: Sampling protocol developed but under re-evaluation to resolve questions about bale sampling and sample drying methodology.
Parameters suggested for sampling protocol:
- Moisture content at sampling should be <18% for burley, 20-25% for dark tobacco.
- Number of leaves per sample for plant sampling should be 30 leaves per sample from 30 different plants, or as many leaves as possible, with no leaves collected from outside plants on stick. Leaves sampled should be the 4th leaf from the top of each plant, with the same leaf sampled within each study.
- For bale sampling, suggest 2 samples of at least 0.7 kg per sample from each 25 kg bale. (Under re-evaluation in current study)
- Whole leaf or lamina only can be used for analysis, as long as a homogeneous ground sample is analyzed. Separation of lamina and midrib suggested for burley, may not be separated for dark and oriental.
- Freeze drying of sample recommended, or air drying with low humidity/dehumidifier. (Under re-evaluation in current study)
- Maximum temperatures for air drying samples should be no more than 30 C.
- Minimum temperature for storing ground samples need not be lower than -18 C.
- At -18 C, storage time for ground samples is not critical. At temperatures higher than -18 C, sample storage time should be as short as possible.
2 Experiments initiated in 2015, will be repeated in 2016:
- Evaluation of bale sampling procedure (Colin Fisher, Univ. of KY), compare core, hand grab, and individual leaf sampling methods for large (200 kg) bales and small (40 kg) bales.
- Evaluation of sample drying procedure (Anne Jack, Univ. of KY), compare air drying, freeze drying, and oven drying.
Objective 4) Collect available TSNA presentations and papers and publish them on the CORESTA website.
TSNA Subgroup Reports
Storage SC report