| Liang-Pan tobacco-growing area (Liangshan City tobacco-growing area and Panzhihua Citytobacco-growing area) is the important strategic high-quality tobacco leaf production base of statetobacco monopoly bureau, which has unique ecological advantages, and have been the maintobacco production area in Sichuan province. Liangshan clear sweet aroma tobacco that producedin Liang-Pan base is the only produce that has access to the national geographical indicationprotection in tobacco industry, and cv. Honghuadajinyuan (hereafter referred as “HD”) is the maincultivated flue-cured tobacco variety in this area. HD has typical fen-flavor style, which waswidely grown, but the acreage fell because of not easy to bulk-cure and poor disease resistance. Inrecent years, the HD was required increased gradually in cigarette formula because of distinctaroma characteristics, excellent quality and well compatibility, and this variety harvested whenappropriate maturity has great influence on the curing and tobacco leaf quality after curing. Thispaper took HD as experimental material and explored the changes of cell ultrastructures, freeamino acids contents, petroleum ether extract contents and neutral volatile aroma substancescontents of tobacco leaves during bulk-curing and the differences of qualities of tobacco leavesafter curing among different harvest period. The main research conclusions are as follows:(1) The changes of cell ultrastructures and organization structure in the process of tobaccoleaf picking and bulk-curing were analyzed, the observation results by electron microscopyshowed that: when harvest, there were differences in the compactness of organelles such aschloroplast with cytoderm, and the size of intercellular space among different grades of maturity;before38℃, the physiological and biochemical reactions were severe in the cell; the yellowingstage(before42℃) was the critical stage of changes of cell physiology and ultrastructure, furtherdegradation of starch and pigmentary substances and improving the organizational structure thequality; In the process of bulk-curing, the leaves of harvesting when optimum ripe compared withmature and over-ripe had advantages of carbohydrate transformation and starch and pigmentary substances degradation to improve the tobacco leaf structure and quality characters.(2) The changes of free amino acids contents in the different grades of maturity tobaccoleaves were analyzed, the results show that the13kinds of amino acids in the tobacco leaves alldecreased by different degrees, but the contents of valine, isoleucine, lysine and proline presented“V” variation trend; The contents of amino acids related to Amadori increased after decreasedwith the increase of maturity degree, but the total free amino acid decreased with the increase ofmaturity degree. In the process of bulk-curing, the contents of free amino acids in mature tobaccoleaves presented inverted “V” variation trend, the maximum appeared at the end of late yellowingor early leaf-drying stages, but the contents of the most of the free amino acids in the optimumripe and over-ripe tobacco leaves increased slightly in the process of bulk-curing; he contents offree amino acids related to Amadori in different treats increased faster at the early yellowing stage,and presented inverted “V” variation trend in the whole curing process; The free amino acidscontents in different treats decreased after increased in the process of bulk-curing.(3) The changes of petroleum ether extract contents in the different grades of maturitytobacco leaves after curing were analyzed, the results showed that: there were highly significantdifferences among different treatments; when tobacco entered into mature stage, petroleum etherextract contents increased obviously with the increase of maturity degree. The differences of etherextract contents among different treats at the end of38℃and48℃reached significant levels inthe process of bulk-curing, and the differences verged to non-significant until the end of curing;The change rules of ether extract contents of different grades of maturity tobacco leaves allpresented increasing trend in the curing process, but had a little difference.Difference analysis results showed that the differences of petroleum ether extract contentamong different maturity treatment were notable, and the petroleum ether extract of the ripe leaveswas significantly higher than that of mature and over-ripe tobacco leaves. Among differentmaturity, the content of petroleum ether extract showed in the order of ripe>mature>over-ripe.(4)Analyzed the different contents of neutral aroma components in different maturity leaves, theresults indicated that, with the maturation, the contents of maillard reaction products and productsdegraded by phenylalanine increased first and then decreased, while the contents of the productsdegraded by cembrance and carotene increase gradually. Neophytadiene contents displayed a trend of rising after the first decline with the maturation, and the contents of overripe leaves were thehighest. In addition to neophytadiene contents, total aroma substances and the neutral componentsincreased with the increase of maturity.The contents of maillard reaction products in different maturity of tobacco leaves duringcuring process presented an ascendant tendency, contents of products degraded by phenylalaninepresented a trend of “N”, the contents of products degraded by cembrance in the mature and ripetobacco leaves showed inverted "V" change trend. At the end of the curing, the cumbrances in theripe leaves were the highest.The contents of products degraded by carotene in different treatmentduring curing process presented rose continued. Except for the neophytadiene, the contents ofother aroma components in the ripe tobacco leaves were highest. Neophytadiene and the totalneutral aroma components contents ascended firstly and then decreased, presenting a trend ofword “V”. The differernce analysis of the aroma components at the end of curing showed that, thecontents of maillard reaction products in the ripe leaves was significantly higher than that inmature and over-ripe leaves, while contents of products degraded by phenylalanine in the matureleaves were highest, which were significantly higher than other treatments. Total contents ofaroma components, except for neophytadiene, showed the following variation trend thatripe>over-ripe> mature. Neophytadiene contents and the total neutral aroma components contentsin the ripe leaves were both higher than other treatments significantly. As for the other aromacomponents, there was no significantly difference among different treatments.(5)Analyzed the effect of different harvest maturities on quality of flue-cured tobacco, theresults showed that: as for the physical properties of tobacco, the weight per leaf and leaf width ofthe mature tobacco leaves were significantly higher than the leaves of the other two treatments,leaf length and leaf thickness of the mature tobacco leaves were significantly higher than that ofover-ripe leaves, but they had no significant difference with the ripe leaves.In the aspect ofchemical compositions, they changed regularly with increase of harvest maturity such as totalsugar, reducing sugar content increased while the starch, nicotine, total nitrogen and proteincontent had the opposite tendency. The chlorine content of the over-ripe tobacco leaves as high as0.14%, which was significantly different with the leaves of other treatments. The potassiumcontent of the ripe leaves was1.95%, which was highest, but it had no significant difference among the different treatments. The chemical coordination of the ripe tobacco leaves presented thebest. In terms of sensory quality, the scores of quality of arom, volume of aroma, offensive odorand sweetness of the ripe tobacco leaves were higher; the score of after taste of the mature leaveswas highest while as to the over-ripe tobacco leaves, score of irritancy was highest. From thecomprehensive performance we could see that the evaluation score of the ripe tobacco leaves wasthe best. |
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