Changes in TSNA contents during tobacco storage and the effect of temperature and nitrate level on TSNA formation.

Samples of burley, sun-cured, and flue-cured tobacco from the main producing areas of relevant tobacco types in China were collected to study the changes in tobacco-specific nitrosamine (TSNA) contents during storage and to investigate the effect of storage temperature and tobacco nitrate level on TSNA formation of cured tobacco. Contents of TSNAs in burley and sun-cured tobacco increased substantially during 1 year under natural storage environment, with total TSNA content increasing about 215% for both tobacco types. The most rapid increase occurred during the high temperature season. Temperature had a significant promoting effect on TSNA formation during storage. Storage temperature as high as 27 °C for 12 days was enough to induce the increase of TSNA formation, while the most significant effect was shown when the temperature was above 30 °C. The increased rate of accumulation became greater as the temperature increased. Total TSNA content in air-cured burley tobacco after the treatment of 60 °C for 24 days was 772% higher than that in the low temperature control. Different types of tobacco showed different results in terms of the response of TSNA formation to high temperature. TSNA formation in flue-cured tobacco did not increase after high-temperature treatment for 36 days, while burley and sun-cured tobacco saw a dramatic increase of TSNA content. This difference could be explained by the fact that burley tobacco and sun-cured tobacco usually had more than 10 times the nitrate content than flue-cured tobacco. As the nitrate nitrogen increased in cured burley tobacco, TSNA formation during leaf storage at high temperature significantly increased. Addition of nitrate onto flue-cured tobacco to the level equivalent to burley tobacco followed by high-temperature treatment increased the TSNA concentration comparable to burley tobacco. The interaction between high temperature and abundant nitrate content in cured tobacco could be responsible for TSNA formation during storage.