Construction And Application Of Curing Process Model Based On Characteristic Parameters Of Fresh Tobacco Leaves

In order to promote the intelligent curing process of tobacco leaves,this experiment was carried out in Lichuan City,Hubei Province from 2019 to 2021.The main characteristics of fresh tobacco leaves were quantitatively analyzed with Yunyan 87,K326,Eyao No.2,HB030 and other tobacco leaves from different parts as experimental materials.According to the results of dark box experiment and curing experiment,the key parameters affecting the color change characteristics and drying characteristics of tobacco leaves were screened,and they were matched with the curing time.At the same time,the corresponding water loss rate model was established according to the drying characteristic parameters of tobacco leaves,and the output model of baking process based on the characteristic parameters of fresh tobacco leaves was finally realized.The main research results are as follows:(1)Screening of main characteristic parameters of fresh tobacco leaves.The research and statistical results showed that the differences of various types of tobacco leaves were mainly concentrated in leaf thickness,whole leaf dry weight,unit leaf area dry weight,leaf width,SPAD value,and main and branch vein width,that is,dry matter accumulation at harvest,maturity and yellowing degree,and leaf shape and vein characteristics were the main differences of different types of tobacco leaves.The SPAD value,whole leaf dry weight and unit leaf area dry weight have great influence on the color change characteristics of tobacco leaves,which can be used as the color change characteristics parameters of fresh tobacco leaves.The leaf thickness,leaf width and leaf vein characteristics of fresh tobacco leaves have significant effects on the dehydration rate during the curing process,which can be used as drying characteristic parameters of fresh tobacco leaves.(2)Fresh tobacco leaf characteristic parameters and baking process parameters match.The research on baking time matching showed that the variation coefficient of baking time at 40 °C was the largest,which was 35.52 %;the variation coefficients at 44 ℃ and 68 °C were 19.24 % and 18.25 %,respectively;the coefficient of variation at 38 °C and 42 °C were 14.35 % and 14.66 %,respectively.Overall,the coefficient of variation of 38 °C ~ 44 °C and 60 °C,68 °C is larger,the coefficient of variation of 46 °C ~ 54 °C is smaller,that is,the focus of baking process matching is yellowing period and dry gluten period.The baking time of yellowing stage can be divided into four categories.The baking time of type I and II is longer at 38 °C.The baking time of type III is nearly equal at 38 ℃ and 40 ℃.The baking time of type IV is longer at 40 ℃.The total baking time is III > IV ≈ II > I.The baking time at dry-gluten stage is directly related to the width of main vein at the base of tobacco leaves,and the general rule is that the baking time at dry-gluten stage increases with the width of main vein at the base of tobacco leaves.In the aspect of temperature and humidity matching,according to the equation of material heating and dehydration in the process of constant speed drying,the corresponding dehydration rate model was established.Through the fitting verification of the actual and predicted dehydration rate of the lower two sheds and the upper two sheds tobacco leaves in each stage of baking,R2 were 0.964 and 0.953,respectively.That is,the model can better reflect the influence of drying characteristics parameters of fresh tobacco leaves and baking temperature and humidity on the dehydration rate of tobacco leaves.At the same time,according to the change of moisture content in baking,the suitable water loss ratio of each stage is roughly: 38 °C-8.31 %,40 °C-14.02 %,42 °C-18.10 %,44 °C-10.40 %,46 °C-8.00 %,48 °C-9.32 %,54 °C-18.74 %,60 °C-7.10 %,68 °C-7.07 %.(3)Construction and application of baking process model based on characteristic parameters of fresh tobacco leaves.Based on the screening of the main characteristic parameters of fresh tobacco leaves and the quantitative matching of the baking process parameters,the baking time discrimination model based on the parameters of fresh tobacco leaves,the calculation model of dehydration amount in each stage of baking based on the moisture content of fresh tobacco leaves,and the water loss rate model of tobacco leaves based on the drying characteristic parameters of fresh tobacco leaves and the temperature and humidity of the bulk curing barn were established.Through the combination of these three models,the baking process operation based on the quality parameters of fresh tobacco leaves can be realized.According to the comparison of the quality of flue-cured tobacco leaves between model baking and conventional baking,the total sugar and reducing sugar contents of flue-cured tobacco leaves under model baking were higher.The grade structure was better.The upper and middle leaf smoke rate was 9.22 % and 7.24 % higher than that of conventional baking,respectively.The orange smoke rate was 8.85 % and 3.74 % higher than that of conventional baking.Under model baking,the average price of middle and upper leaves was increased by 2.18 yuan / kg and 0.82 yuan / kg,respectively.The smoking evaluation results showed that under the model baking mode,in addition to combustibility and ash content,the scores of aroma quality,aroma quantity and other indicators were improved,and the total smoking evaluation scores of C3 F and B2 F were 1.9 and 1.7 higher than those of conventional baking,respectively.