Study On Changes Of Water Content And Electrical Charactristics Of Flue-cured Tobacco Leaves And Wind Speed Between Flue-cured Tobacco Leaves In Bulk-curing Barn

In order to provide scientific basis for optimization of curing technology andexplore the detection indexes of intelligent bulk curing controller and evaluationinstrument of grade of tobacco，this paper studied the change laws of water contentand electrical characteristics of tobacco leaf, the relationship among water content,electrical characteristics, tissue structure, color parameters, pigment content, contentsof main chemical components, leaf morphology and leaf specific weight of tobaccoleaf, the relationship between capacitance value of tobacco leaf and grade of tobaccoand the change law of wind speed between tobacco leaves of different levels in bulkcuring barn, with the methods of sampling at key temperatures in bulk-curing andperiodic determination of wind speed between tobacco leaves in bulk curing barn. Itsmain results are as follows:1. Dynamic change of water content of tobacco leaf and the relationshipbetween leaf water content and physical and chemical properties of tobacco leafThere was a close relationship between the lost water of tobacco leaf andflue-curing process, and the proportion of lost weight of tobacco leaf water to the totallost weight of tobacco leaf water was respectively40.27%,56.31%and3.42%inyellowing stage, color fixing stage and stem drying stage.The water loss speed value reached the maximum, which was3.44%/℃, and thewater loss speed value was respectively2.46%/℃and0.18%/℃in yellowing stageand stem drying stage.There were very significant correlations between water content and leafthickness, between water content and upper epidermis thickness, between watercontent and palisade tissue thickness, between water content and spongy tissuethickness, between water content and front side L*value, between water content andfront side a~*value, between water content and back side L~*value, between watercontent and back side a~*value, between water content and H value, between water content and chlorophyll-a content, between water content and chlorophyll-b content,between water content and β-carotene content, between water content andxanthophylls content, between water content and neoxanthin content, between watercontent and starch content, between water content and total nitrogen, between watercontent and protein content, between water content and cellulose content, betweenwater content and total sugar content, between water content and reducing sugarcontent, between water content and longitudinal shrinkage, between water content andtransverse shrinkage, between water content and area shrinkage, between watercontent and thickness shrinkage, and between water content and leaf specific weight,and the correlation coefficients were respectively0.969,0.955,0.954,0.934,-0.946,-0.976,-0.834,-0.968,0.950,0.833,0.851,0.984,0.924,0.951,0.810,0.902、0.945,0.900,-0.880,-0.818,-0.983,-0.971,-0.990,-0.974and0.949.But there were not significant correlations between water content and front sideb*value, between water content and back side b~*value, between water content and Cvalue, and between water content and total pectin content, the mathematical modelbetween water content (X) and leaf specific weight (Y) was linear equation: Y=0.0102+0.0002X (R~2=0.901).2. The optimal determination mode and frequency of capacitance of tobaccoleaf.1K Hz capacitance (R~2=0.9875) whose R~2value of fitting equation test value wasbigger and whose frequency was smaller, was the optimal determination frequency ofcapacitance of tobacco leaf,10K Hz capacitance was the second one, and100K Hzcapacitance was the third one.When the determination frequency of capacitance of tobacco leaf was1K Hz, theR~2value (0.9875) of parallel mode was more than the R~2value (0.9846) of seriesmode, so parallel mode was determined as the optimal determination mode ofcapacitance of tobacco leaf.3. The change law of electrical characteristics of tobacco leaf and therelationship between electrical characteristics of tobacco leaf and physical andchemical properties of tobacco leaf.The capacitance value of tobacco leaf decreased gradually with the process ofbulk-curing, and the mathematical model between water content (X) and capacitancevalue (Y) was linear equation: Y=1.685+0.020X (R~2=0.938), but also There was verysignificant correlation between water content and capacitance value (r=0.969). The resistance value of tobacco leaf increased gradually with the process ofbulk-curing, after42℃the resistance value of tobacco leaf increased rapid, and after54℃it was very large even infinite. The relationship between resistance value andwater content was a significant negative correlation (r=-0.845), and the mathematicalmodel between water content (X) and resistance value (Y) was curve equation: Y=1716.893-80.649X+1.259X~2-0.006X~3(R~2=0.714).There were very significant correlations between capacitance value and leafthickness, between capacitance value and upper epidermis thickness, betweencapacitance value and palisade tissue thickness, between capacitance value andspongy tissue thickness, between capacitance value and front side L~*value, betweencapacitance value and front side a~*value, between capacitance value and back side L~*value, between capacitance value and back side a~*value, between capacitance valueand H value, between capacitance value and chlorophyll-a content, betweencapacitance value and chlorophyll-b content, between capacitance value andβ-carotene content, between capacitance value and xanthophylls content, betweencapacitance value and neoxanthin content, between capacitance value and starchcontent, between capacitance value and total nitrogen, between capacitance value andprotein content, between capacitance value and cellulose content, betweencapacitance value and total sugar content, between capacitance value and reducingsugar content, between capacitance value and soluble pectin content, betweencapacitance value and longitudinal shrinkage, between capacitance value andtransverse shrinkage, between capacitance value and area shrinkage, betweencapacitance value and thickness shrinkage, and between capacitance value and leafspecific weight, and the correlation coefficients were respectively0.991,0.973,0.993,0.980,-0.981,-0.924,-0.876,-0.915,0.863,0.885,0.903,0.938,0.938,0.967,0.856,0.861,0.855,0.897,0.890,-0.916,-0.865,-0.870,-0.992,-0.930,-0.974,-0.986and0.945.There were significant correlations between capacitance value and back side b~*value, between capacitance value and C value, and between capacitance value andpetroleum ether extract content, and the correlation coefficients wererespectively-0.695,-0.727and-0.771.But there were not significant correlations between capacitance value and frontside b~*value, and between capacitance value and total pectin content, the capacitancevalue of tobacco leaf increased gradually when leaf specific weight increased, and the mathematical model between leaf specific weight (X) and capacitance value (Y) waslinear equation: Y=0.660+107.053X (R~2=0.893).There were very significant correlations between resistance value and H, andbetween resistance value and petroleum ether extract content, and the correlationcoefficients were respectively-0.917,0.957, there were significant correlationsbetween resistance value and front side a~*value, between resistance value and backside a~*value, between resistance value and β-carotene content, between resistancevalue and total nitrogen content, between resistance value and protein content,between resistance value and transverse shrinkage, between resistance value and areashrinkage, and the correlation coefficients were respectively0.834,0.817,-0.835,-0.767,-0.766,0.868and0.806, But there were not significant correlations betweenresistance value and other indexes.4. The relationship of tobacco grade and electrical characteristics of tobaccoleaf.With the rising of leaf location, the capacitance value of tobacco leaf increased.In color group and slick group, the capacitance value of tobacco leaf of red group wasthe maximum, followed by slick group, greenish group, variegated group, orangegroup, lemon group and green-yellow group. In the same group, with the promotionof tobacco grade, the capacitance value of tobacco leaf increased.5. The factors and laws of influence the capacitance value of tobacco leaf.In the bulk-curing process, before48℃the capacitance value of tobacco leafincreased with the promotion of tobacco leaf maturity, while after48℃thecapacitance value of tobacco leaf showed as mature＞ripe＞unripe, and thecapacitance value of overripe tobacco leaf was the minimum in the whole bulk-curingprocess.With the time of tobacco leaf air-curing being longer, the capacitance value oftobacco leaf decreased correspondingly. In the bulk-curing process, before38℃theinfluence of flue-cured tobacco variety on capacitance value was great, after38℃theinfluence was opposite.In the earlier stage of the bulk-curing process, with the fan frequency increasing,the capacitance value of tobacco leaf decreased correspondingly. The influence of fanfrequency on capacitance value in the earlier stage was more than it in later stage.With the fan frequency increasing in the whole bulk-curing process, the capacitancevalue of cured tobacco leaf increased correspondingly. In the bulk-curing process, the resistance value of tobacco leaf increased with thepromotion of tobacco leaf maturity. With the time of tobacco leaf air-curing beinglonger, the resistance value of tobacco leaf increased correspondingly.The influence of flue-cured tobacco variety on resistance value before38℃wasmore than it after38℃.In the earlier stage of the bulk-curing process, with the fan frequency increasing,the resistance value of tobacco leaf increased correspondingly. The influence of fanfrequency on resistance value in the later stage was more than it in earlier stage. Withthe fan frequency increasing in the whole bulk-curing process, the resistance value ofcured tobacco leaf increased correspondingly.6. The changes of wind speed between tobacco leaves in the bulk barn.The diversity of wind speed indexes between tobacco leaves within differentspots on the same plane in the bulk barn was lesser and even was regarded as uniformand indistinctive. So the bulk barn could guarantee that tobacco leaves of the sameplane in the leaf-room the same plane were at the same color-changing andleaf-drying condition in the whole and thereby could afford a guarantee for the samecured quality of tobacco leaves of the same plane in the leaf-room theoretically.In the air rising type bulk curing barn, as for different levels of barn, the windspeed values of bottom level in yellowing stage, color fixing stage and stem dryingstage were maximum (they were respectively0.2738m/s,0.3450m/s and0.3804m/s),and followed by wind speed values of middle level (they were respectively0.1963m/s,0.2458m/s and0.2819m/s) and wind speed values of top level (they were respectively0.1596m/s,0.1971m/s and0.2793m/s). The wind speed of the bottom level wassignificant difference to that of the middle and top levels in stem drying stage, but itwas extremely significantly different in yellowing stage, and the wind speed of thebottom level was significant difference to that of the middle level in color fixing stage,while the wind speed of the bottom level was extremely significant difference to thatof top level in color fixing stage, and there was no significant difference between thewind speed of the middle level and the wind speed of the top level in the whole curingprocess.As for different stages of bulk curing process, the wind speed values of bottomlevel, middle level and top level of barn in yellowing stage were minimums, followedby color fixing stage and stem drying stage. The wind speed values of bottom leveland middle level of barn in yellowing stage were significant difference to it in stem drying stage, but the wind speed values of top level of barn in yellowing stage werevery significant difference to it in stem drying stage. The wind speed values ofdifferent levels of barn in yellowing stage were not significant difference to it in colorfixing stage. The wind speed value of top level of barn in color fixing stage were verysignificant difference to it in stem drying stage, but the wind speed values of otherlevels of barn in color fixing stage were not significant difference to it in stem dryingstage.With the bulk curing, the variation of wind speed of top level was morecomplicated than the middle and bottom levels in barn. For every stage of bulk curingprocess, the influence for the variation of wind speeds of barn in the yellowing andcolor fixing stage were more significant than it in stem drying stage.To sum up, in bulk curing process:1) the proportion of lost weight of tobaccoleaf water in the yellowing and color fixing stage to the total lost weight of tobaccoleaf water in the whole bulk curing process was more than95%, and the water lossspeed values of tobacco leaf in yellowing stage and color fixing stage were muchlarger than it in stem drying stage. There was a close relationship among the water oftobacco leaf, tissue structure, color parameters, pigment content, contents of mainchemical components, leaf morphology and leaf specific weight of tobacco leaf.2)with the water content of tobacco leaf decreasing, capacitance value of tobacco leafdecreasing significantly, but resistance value of tobacco leaf increased significantlyand correspondingly.3) there was a close relationship among the capacitance value oftobacco leaf, tissue structure, color parameters, pigment content, contents of mainchemical components, leaf morphology and leaf specific weight of tobacco leaf, butthere was a close relationship between resistance value of tobacco leaf and a few ofindexes of color parameters, pigment content, contents of main chemical componentsand leaf morphology of tobacco leaf.4) in bulk curing process, the capacitance valueof tobacco leaf could reflect factually changes of physiology, biochemistry andphysical property of tobacco leaf, so it could be as a detection index of intelligent bulkcuring controller.5) there a certain relationship between capacitance value of tobaccoleaf and grade of tobacco, and if a further study on the internal relation between them,capacitance value of tobacco leaf might be a detection index of evaluation instrumentof grade of tobacco.6) the bulk barn could afford a guarantee for the uniform andindistinctive wind speeds of tobacco leaves of very plane in barn. In the air rising typebulk curing barn, the wind speed value of tobacco leaves of bottom level was maximum, followed by middle level and top level, while the wind speed value oftobacco leaves in stem drying stage, followed by color fixing stage and yellowingstage.