@article{abubakar_young_johnson_weeks_2003, title={Modeling moisture and chemical changes during bulk curing of flue-cured tobacco}, volume={46}, DOI={10.13031/2013.13935}, abstractNote={Mathematical models to predict moisture content, chlorophyll, starch, and reducing sugar concentrations were 
developed as a function of curing variables like temperature, initial moisture content, airflow rate, time, and initial chemical 
concentrations. The moisture removal model was based on a two–term (liquid and vapor) thin–layer drying equation, while 
chlorophyll, starch, and respiration models were based on first–order rate equations. Several product parameters required 
in secondary equations were determined through regression and comparison of root mean square errors. The models were 
fitted to the experimental data collected during the first year of the experiments (1997) to determine the product parameters 
by minimizing root mean square errors. The models were then verified using the experimental data obtained in the second 
year of the experiments. The models will help predict effects of curing variables on rate of moisture removal and chemical 
concentrations in the cured tobacco leaf. This information will contribute to the optimization of the curing process in terms 
of process efficiency and product quality.}, number={4}, journal={Transactions of the ASAE}, author={Abubakar, Y. and Young, J. H. and Johnson, W. H. and Weeks, W. W.}, year={2003}, pages={1123–1134} }
 @article{weeks_campos_moldoveanu_1993, title={BIOCHEMICAL AND MODEL CHEMICAL-REACTIONS FOR THE BASIS OF RED PIGMENT IN FLUE-CURED TOBACCO}, volume={41}, ISSN={["0021-8561"]}, DOI={10.1021/jf00032a030}, abstractNote={Polyphenol oxidase (PPO) preparations from green tobacco leaves oxidized chlorogenic and caffeic acids to o-quinones, which reacted in vitro with nornicotine to produce red color at 570 nm. Activity was not obtained when ferulic acid was used as a substrate. Variable temperature data showed PPO was stable for 1 h at 75 degrees C. Nicotine, myosmine, pyrrolidine, asparagine, alanine, and glutamic acid failed to react with chlorogenic acid and enzyme; nor did these compounds interfere with color development between nornicotine and o-quinones. Aqueous ethanolic extracts (80%) gave similar red color from tobacco grade FR and cherry red tobacco (CR) but a brown color from orange tobacco grade F. Alkaloid analysis showed CR and FR grade tobaccos contained higher levels of nornicotine than F grade tobacco. Model chemical reactions with nornicotine showed coupling of nornicotine with o- and p-quinones by Schiff base and Michael addition reaction.}, number={8}, journal={JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY}, author={WEEKS, WW and CAMPOS, MP and MOLDOVEANU, S}, year={1993}, month={Aug}, pages={1321–1328} }