TSNAs contents in lamina and midrib of flue-cured tobacco and their changes after high temperature storage

Thirty flue-cured tobacco samples from Henan, Yunnan, Guizhou, Hunan and Guangdong were collected and a variety test was set up in Luoyang, Henan province to investigate the relationship between TSNAs content and their precursors in flue-cured tobacco lamina and midrib, and effect of geographic location, variety and leaf position on this relationship. Flue-cured tobacco lamina and midrib were stored at 50℃ to study the effect of high temperature storage on contents of TSNAs, alkaloid and nitrate. Results showed that content of TSNAs in flue-cured tobacco lamina was significantly higher than in midrib, and the highest proportion in lamina was NNN, whereas the highest percentage in midrib was NNK. Total alkaloids in lamina were about 4.7 times higher than in midrib. Nitrate content in midrib was higher than in lamina. TSNAs content in lamina varies significantly between regions, with the highest content in Hunan and Guangdong. Significant differences were found in TSNAs content of lamina between varieties, and the changes of TSNAs were closely related with alkaloid content. Lamina had the highest TSNAs content, followed by side-vein and mid-vein. Correlation analysis revealed that accumulation of TSNAs in tobacco was mainly affected by amount of alkaloid accumulated during flue-curing. TSNAs content of midrib and lamina under 50℃ storage increased 229.2% and 30.6%, respectively, compared with that in low temperature, suggesting that nitrate levels had greater influence on TSNAs formation during high temperature storage.