| Storage is an important process to reduce the impurities and irritation of original tobacco,it is also important to improve the quality of tobacco leaves and smoke.Generally,the best time for this process is 2-3 years,however,in the actual production process,due to industrial pressure and other reasons,it needs to be extended to more than 5 years.During this period,the changes of harmful components and aroma of tobacco leaves are not clear.Samples of Yunnan Binchuan,Henan Baofeng flue-cured tobacco,Sichuan Xuanhan,Yunnan Binchuan Burley tobacco and Sichuan Wanyuan sun-cured tobacco which stored under natural conditions in National Tobacco Cultivation Physiological and Biochemical Research Base of Henan Agricultural University were collected regularly to investigate changes in content of TSNAs,alkaloid,nitrate and neutral aroma components during storage in order to clarify the changing rules of tobacco specific nitrosamines and neutral aroma components during long-term storage of different types of tobacco leaves,and to provide theoretical basis for rational storage of tobacco leaves,ensuring the safety of tobacco leaves and improving the quality of tobacco.The content of TSNAs was detected by SPE-LC-MS/MS method,and the content of neutral aroma components was detected by LC-GC method.The results of this study are as follows:1.With the increase of storage time,the contents of NNN,NNK,NAB,NAT and total TSNAs of flue-cured tobacco,burley tobacco and sun-cured tobacco all showed an increasing trend,Burley tobacco increased the most and the total TSNAs of burley tobacco increased 771.55%after storage.NNN increase by 45442.23ng/g and total TSNAs increase by 54344.16 ng/g in Sichuan Xuanhan burley tobacco which increase was the highest;The second is sun-cured,the total TSNAs increased by 358.62%compared with before storage,flue-cured tobacco content only fluctuated in a small range during storage,which increase trend is not obvious.The NNN and total TSNAs content of Sichuan and Yunnan burley tobacco were the highest,The NNK content in sun-cured tobacco was the highest.The NAB and NAT content in Sichuan Burley tobacco was the highest,and the difference between regions was obvious.2.With the increase of storage time,the alkaloids and nitrates contents in three types of tobacco leaves decreased.The nicotine content in Sichuan Wanyuan sun-cured tobacco decreased greatly,and the nornicotine and total alkaloid content in Sichuan burley tobacco decreased the most.The decrease of anabasine content in Yunnan flue-cured tobacco and the decrease of anatabine content in Yunnan burley tobacco was greater.The reduction rate of nitrate was the highest in Sichuan sun-cured tobacco,and the nitrate reduction in Sichuan burley tobacco was more.The contents of nicotine,anabasine and anatabine in Sichuan sun-cured tobacco were the highest,nornicotine and total alkaloids in burley tobacco were the highest,especially in Sichuan burley tobacco.Nitrate content varied greatly among different types of tobacco,the average content of burley tobacco was 3976.36?g/g before storage,which was 96.63 times higher than that of Flue-cured tobacco at 41.15?g/g,and it was also 159.28 times after storage?3.The TSNAs content of tobacco leaves during storage was correlated with alkaloid and nitrate,among them,NNN and nornicotine,NNK and nicotine,NAB and anabasine,NAT and anatabine,total TSNAs and total alkaloids,TSNAs and nitrate were highly correlated and nitrate which was more closely related to the TSNAs content after storage than that before storage was more closely associated with TSNAs formation,alkaloids are opposite.4.There were significant differences in the content of main ketone aroma components in the three types of tobacco leaves.The total amount of burley ketone ketones was 46.251 ?g/g,followed by sun-cured tobacco at40.053 ?g/g,and the content in flue-cured tobacco which was at 26.306 ?g/g was lowest.5.The three types of tobacco ketones have different trends in aroma components.Meg,Geranylacetone,Dihydroactinidiolide,3-OH-damasone,Ionone oxide showed a trend of rise-fall are degradation products of carotenoid,as well as the beta-Ionone which decreased during storage.The contents of Solanone and Norsolandione which are the degradation products of cembranoid decreased,too.6.Meg,Solanone,Ionone oxide contents of burley tobacco were the highest and had the long rising time,the peak appeared in 60.95 months.Geranylacetone and beta-Ionone contents of sun-cured tobacco was the highest and the peak appeared in 47.98 months.,3-OH-damasone and Norsolandione contents of flue-cured tobacco were the highest and the peak appeared in 37.59 months.7.The changes of TSNAs,alkaloids,nitrates and main volatile aroma of ketones in tobacco leaves are fitted to the quadratic curve model.8.The longer the storage time,the more the TSNAs are produced,the lower the safety of tobacco leaves,and the aroma substances will decrease in the later stage of storage,resulting in insufficient aroma and bad quality of the tobacco leaves.Therefore,it is necessary to properly control the storage time,flue-cured tobacco,burley tobacco and sun-cured tobacco are suitable for different aging periods.The storage stability of flue-cured tobacco is worse than that of burley tobacco and sun-cured tobacco.So the storage of flue-cured tobacco should not exceed 30 months,and the storage time of burley tobacco and sun-cured tobacco should be controlled at about 60 months. |
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