| Thirty flue-cured tobacco samples produced in 3 producing areas of china(Henan,Yunnan-guizhou and Hunan-guangdong)were collected and a variety test set up in Luoyang,Henan province to investigate the relationship between TSNAs content and their precursors of flue-cured tobacco lamina and midrib in different regions,different varieties and different parts.In addition,the flue-cured tobacco lamina and midrib were stored at 50 and natural storage to study the effect of storage on the contents of TSNAs,℃ alkaloid and nitrate.Results showed that:(1)the content of TSNAs in flue-cured tobacco lamina were significantly higher than that in tobacco midrib,and the highest proportion in lamina was NNN,whereas the highest percentage in the midrib was NNK.Total alkaloids in the lamina were higher than midrib with the mean values of 3.235% and in midrib was 0.692%,which was about 4.7 times of midrib;Nitrate content in tobacco midrib was higher with the content of 680.25μg/g compared to 23.679μg/g in the lamina.Relevant analysis revealed that the content of TSNA had significantly positive correlation with alkaloid levels,and correlation coefficient between nitrate and TSNA was quite small,which indicated that accumulation of TSNA in tobacco was mainly affected by the amount of alkaloid accumulated during flue-curing.(2)TSNAs content in lamina were significantly different between regions,with the highest content in Hunan-Guangdong,and the lowest content in Yunnan-guizhou,The alkaloids content in tobacco lamina was the same trend;Furthermore,significant differences were found in TSNAs content of lamina between different varieties,and the changes of TSNAs have close relationship with alkaloid content.(3)Within tobacco leaves,Upper leaves had the highest TSNAs concentration,followed by middle and lower leaves,the alkaloids was the same trend,lower leaves had the highest nitrate concentration,followed by middle and upper leaves;Within a tobacco leaf,the lamina has the highest TSNAs concentration,followed by side-vein and mid-vein,the alkaloids contend was leaf>side-vein>mid-vein,the mid-vein has the highest nitrate contend.(4)Tobacco Maturity had effect on cell membrane permeability and alkaloid,NO3-andNO2-contend[1],The content of TSNAs in tobacco leaves with different maturity was immature leaf,immature ripe and over mature.(5)After 50 storage the increase magnitude of TSNA content in lamina have obvious ℃difference with that in midrib.And the TSNA content of midrib and lamina increased 229.25% and 30.55%,The nitrate content in the lamina was much lower than that of the tobacco midrib,and the amount of nitrate in tobacco midrib was 23 times higher than that in the lamina after storage at high temperature,respectively,compared with that in low temperature control,suggesting that nitrate levels had a much greater influence on TSNAs formation during high temperature storage.(6)The content of TSNAs in flue-cured tobacco after natural storage were significantly increased and which was higher than high temperature storage,The content of TSNAs in lamina increased higher than the high temperature storage by 13.64%,tobacco midrib increased by 76.98%,Therefore,the storage period of tobacco leaves is an important stage of TSNA formation.(7)The experimental research on the different humidity set 4 humidity gradient which were 6.8%,10.6%,14.5%,23.1%,the regression analysis shows that there is a linear relationship between the total TSNAs and humidity,and it will be described as a formula of the y=-4.35x+343.87,it means that with the increase of humidity,the content of tobacco specific nitrosamines decreased during storage,temperature and humidity become an important factor affecting the formation of TSNAs. |
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