Changes of Cell Ultrastructure and Physiological Indexes and Physical Properties of Tobacco Leaves during Bulk Flue-Curing
|School||Henan Agricultural University|
|Keywords||Flue-cured tobacco Bulk flue-curing Nanometer paint Phys-iological indexes Physical properties Colour Texture Cell way Ultrastructure|
In order to provide theoretical basis for optimization and perfection of curing technology, using New NC89, Zhongyan100 and Qinyan96 as material, at the key temperature points (fresh, 38℃, 42℃, 48℃, 54℃, dry sample) the changes of physiological indexes, colour, and related physiological indexes of tobacco leaves were studied while changes of cell ultrastructure were observed by Hitachi H-600 Electron Microscope during the bulk curing using the electric-heated flue-curing barn. Its main conclusion is as follows.1. The solube pectin content had been on the rise as degradation of protopectin, total pectin and cellulose contents of the New NC89 tobacco leaves during the flue-curing process. Correlation analysis showed that the relationship of pectin (total pectin, protopectin and solube pectin) with PG was more closely than that with the PME. PG was more helpful to hydrolysis cell way and inhibt the formation of the glossy leaves than others. At 38～48℃, especially at 42℃prolong curing time, create the sutiable curing environmental condition, keep higher enzymes activities of cell way, provoke cell way substances and macromolecules to degradate and converte sufficiently according to the changes of the cell way enzymes activities and the cell way substances, which would be beneficial to the occurrence of the physiological biochemical responses, inhibt the formation of the glossy leaves and improve the quality and benefit of the tobacco production.2. The peaks of the pectin methylesterase, polygalacturonase and cellulase activities of the nano treatment appeared at 42℃, 48℃and 38℃respectively. The peaks of the PG and cellulase activities were ahead of CK among them, but the enzymes activities of cell way were lower than CK in the later curing. The content of cellulose of treatment was always obviously higher than CK and the cured sample of treatment was 12 mg/g higher than CK. The content of soluble pectin, protopectin and total pectin of treatment was also obviously higher than CK after 42℃. The highest content of total pectin of treatment was 6.34% at 42℃. High class leaf and total output value of treatment increased by 7.33%, 16.56 % than CK respectively and the differences between them were all highly significant. At the same time the weight per leaf was 0.71 g higher than CK and the difference was significant. Nano coating had a great effect on enzymes activities and components of cell way and economic characters of upper leaves. The result showed that it could improve economic benefit. It provided reference for applying further in curing technology on basis of the functions of nano coating and the change rule of cell physiological and biochemical reactions of the New NC89 tobacco leaves with treatment.3. The contents of the starch, chlorophyll and carotenoids of Zhongyan100 tobacco leaves changed greatly in the early yellowing stage; the differences of moisture content, thickness, density of tobacco leaves in the yellowing and leaf-drying stages were highly significant; the contents of the pectin and cellulose changed mainly in the leaf-drying stage; but leaf specific weight changed little relatively during flue-curing. Cell ultrastructure observation indicated that cell way, chloroplast and nucleus changed obviously, but mitochondrias were not easy to be found during flue-curing. The cell structure of the fresh leaves is normal, but chromatin decreased and part of the nuclear membrane disappeared at 38℃; cells showed plasmolysis, chloroplast and other cellular organs freed to the central cell, chloroplast outer membrane and nuclear membrane fractured, most osmiophilic granules presented half-hollow state, grana lamella and most starch grains disappeared at 42℃; the obvious twist distortion of cell way and nucleus pyknosis appeared at 48℃; individual shapes of chloroplast were not apt to differentiate and the remains was basically osmiophilic material of the weak electronic density after 54℃. It was helpful to enhance the content of the oligosaccharides, monosaccharides, aroma matter and improve organization structure with the appearance quality of tobacco leaves at the following measures. Firstly, prolong the time at 38℃in the yellowing stages and make the starch, pigments and so on in the chloroplast degradated fully. Secondly, regulate the process of flue-cuing rationally in the leaf-drying stages and decrease the content of the cell way substances. The changes of the cell ultrastructure of tobacco leaves was closely related to identity and physiological and biochemical reactions and extent of degradation and transformation of inclusion during flue-curing. It could provide theoretical basis for optimizing of curing technology and improving tobacco quality according to these.4. Texture and color parameters of Zhongyan100 tobacco leaves (not including midrib) changed greatly around 38℃in the yellowing stage during bulk-curing process. Texture and color parameters of midrib of tobacco leaves changed greatly after 42℃, especially at 48~54℃. The dynamic changes of texture parameters curve including hardness, resilience and chewiness of tobacco leaves were intuitive in the texture profile analysis test during bulk-curing. Differences of all color parameters of tobacco leaves were highly significant (P<0.01) during bulk-curing and the difference of a* was more significant than b*. At the same time the differences of color of tobacco leaves (not including midrib) were more visible than midrib’. Correlation analysis showed that correlation of texture parameters of tobacco leaves (not including midrib) including hardness, resilience and chewiness was better (0.952~0.992) and they were reliability index on evaluation the test of texture profile analysis. Texture of midrib of tobacco leaves was sensitively reflected by cohesiveness and resilience. Compared with midrib, correlation of color parameters of tobacco leaves (not including midrib) was better (0.852~0.962) and positive significant or highly significant. Correlation between L* and a* was better than L* with b*’from correlation analysis of color parameters.5. The texture parameters of Zhongyan100 tobacco leaves changed greatly while the cell way enzymes were in the high activity and cell way substances with moisture changed greatly at 38~48℃. The texture of tobacco leaves became mealy just for the result of the decrease of the cell binding force in a way during flue-curing. In other words, it could result from the constant degradation of cell way substances. Dynamic change of shear force parameter was more intuitive. The main factors to make a significant difference of texture of tobacco leaves were the change of cell physiology during flue-curing. Regulating the process of flue-cuing rationally in the yellowing stages when the tobacco leaves collapse and turn yellow at 80 percent around, prolonging the curing time at 42℃, integrating with differences of the apperences of leaves, rejusting the curing process and environments, making the resilience and tensile value lower, which could decrease the content of the cell way substances and inhibit formation of the dense structure.6. Compared with Zhongyan100, the moisture content of Qinyan96 tobacco leaves was higher at 38~54℃, the activities of peroxidase (POD) were higher while the activities of lipoxygenase (LOX) were lower in the yellowing stage, while the textural parameters values were larger. But the leaf-drying stage showed a contrary tendency. After the leaf-drying stage 48℃colour parameters showed better. During the flue-curing the change of textural and colour parameters of Qinyan96 tobacco leaves were significant difference and pigment degradation was more fully than Zhongyan100. Correlation analysis showed that correlations of colour parameters were better during the curing process (｜R｜= 0.677~0.997), so were correlations of colour parameters with pigment (｜R｜= 0.661~0.973). Correlation between hardness and chewiness was highly significant positive (P<0.01); correlations of resilience with a*、H were highly significant (P<0.05); correlations of cohesiveness with L*、b*、C* were significant or highly significant negative (P<0.05). Therefore, the four textural parameters and five colour parameters were all feasible to study the change of tobacco leaves during the flue-curing. The texture of cured tobacco leaves of Qinyan96 was looser and the colour was better in the late curing stage. This study provided theoretical basis for quantitative real-time monitoring of texture and colour parameters change of tobacco leaves during the flue-curing.7. Compared with Zhongyan100, the cell way substances of Qinyan96 tobacco leaves was degrade early, and pigments and starch in the chloroplast was degrade fully during the flue-curing. Compared with Zhongyan100, the content of the pigments and starch was lower during the late flue-curing. Cell way of the Zhongyan100 leaves was twisted early during the flue-curing meanwhile cell physiological and biochemical responses of tobacco leaves was inhibited early. The degradation of the inner substances of tobacco leaves was inhibited to a certain extent. This showed that physiological and biochemical reactions and its level was closely related to the changes of cell ultrastructure. Also, it was an important factor to lead the differences of Zhongyan100 and Qinyan96 at the same maturity.8. The activities of POD were higher while respiration, the activities of LOX and cell way enzymes were lower in the yellowing stage (38~42℃). That could make the tobacco leaves lost water properly, and extend the life of the leaves. On the contrary, the measures would be taken in the leaf-drying stage (42~54℃). Pigment and cell way substances would be fully degradated and converted. Also, the content of the aroma matter would be enhanced and organization structure would be improved. The measures would be taken for Zhongyan100 that prolong the time, enhance the moisture of leaves and protective function of the organization cell in the yellowing stages. At last, the pigments could be fully degradated.9. By adjusting the curing ban environments of the temperature with humidity and process during the flue-curing, pigment and cell wall substances were degradated fully around 48℃, organizational structure was damaged properly, value of the hardness, chewness, resilience, shear force, tensile was drop. Afer that texture of tobacco leaves was improved. It was helpful for dropping in dense degree for Zhongyan100 that kept the higher activities of POD before 42℃, reduced the damage of cell membranes and made macromolecular substances degradate and transform fully.10. On one hand, appearance and colour related to conditions of temperature and humidity during the flue-curing. On the other hand, it was relevant to the degree of degradation and conversion and the proportion of chlorophyll and carotenoids of tobacco leaves during the flue-curing. The relatively high humidity would help deepen orange concentration (increase a value) of tobacco leaves after 60℃. It should improve wet temperature (42~43℃) for Zhongyan100 during this period. Besides, flue-curing process was reasonably regulated while the hungry metabolism sustained longer. It would make pigments substances degradate and transform fully, and improve tobacco appearance colour. The difference of dry sample tobacco leaves between Qinyan96 and Zhongyan100 was consistent with difference of tobacco leaves during the flue-curing. In other words, the formation of cured tobacco leaves qualities was originated from the accumulation of qualities factors in the process of flue-curing.