| The aroma compounds are closely related to human smoking behavior and tobacco product quality. The aroma of tobacco leaf is one of the most important factors in evalution of its quality. And tobacco quality has a direct impact on the smoking and sensory quality. However, the tobacco conponents are so complex that it is a big challenge to study the compounds. The aroma style of different tobacco types is depended on its aroma compositions. Tobacco leaf flavors are known to consist of a variety of odorant eliciting very different flavor attributes, such as floral, sweet, toast and so on. However, when present in certain quantities, these odorants create the characteristic smell associated with a certain tobacco variety. There are thousands of compounds in tobacco leaves have been identified, whereas some aroma compoungds have not been found so far, this is due to their extremely low concentrations, such odorants are very difficult to monitor by use of common analytical methodologies such as GC-MS, etc.To gain a deeper insight into the aroma style of different tobacco leaves and provide guide for aroma regulation technique, Gas Chromatography-Mass Spectra/Olfactory(GC-MS/O) was applied in this dissertation. GC-MS/O is a powerful way in screening aroma compounds in tobacco leaves effectively, which was combined GC-MS to Olfactory. The following several parts were completed.1. Optimization of analytical methods based on the known one. First, by comparison the two traditional methods:simultaneous distillation extraction and solvent extraction. The results showed that SDE is prior to SE from the view of extraction efficiency. But it’s not benefit for the assessor because the more aroma compounds were perceived, the more easily assessor became tired. It maybe the high temperature during SDE, leads to some by-products whose smell impact the original aroma of tobacco leaf. SE was a better selection because of mild condition. Second, Took slower temperature rate. It is not only good for the isolation of compounds, but also benefits to assessor. Third, assessor was trained systematically according to the international standard.2. Compared the differences of three types tobacco leaves with removing nicotine, in order to avoid the impact of nicotine. The results of GC-MS/O showed that the most significant impact is the sour taste became stronger because of some acids whose content increased, some alkali decreased. At the same time, the neutral compounds have no clearly chage both in content and flavor. So, nicotine was removed by tartaric acid which is suitable to the GC-MS/O.3. The aroma zone can be classified into two zones according to the GC-MS/O analysis. The flavor was green, pungent before30min, and it became floural, sweet and comfortable after the point. The key aroma compounds were identified by combined intensity method with AEDA in aroma zone, whose aromatic characteristics are pleasure. At last, from the view of aroma intensity and FD factor, we found that the key aroma compounds in three different tobacco leaves are a little different. The key aroma compounds are β-damascenone and β-damascone in Fule-cured tobacco; β-damascenone, β-damascone and megastigmatrienone4+Unknown in Burley tobacco; β-damascenone, β-damascone and methyleugenol in Oriential tobacco. The fact is that the key aroma compounds are not the high concentration compounds, all datum confirm earlier results of the literature on the key role of solanone, geranylacetone, dihydroactinidiolide etc. In addition, methyleugenol, β-damascone, and the unknown compounds are suggested as further key tobacco aroma compounds. There isn’t one tobacco leaf aroma can be assigned to single aroma compounds. |
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