Effect Of Maturity On Tobacco Leaf Color, Biochemical Changes During The Flue-curing Process And Post-curing Qualit

To find the optimal harvesting maturity of Guizhou Yunya 87 central leaves,and to investigate the correlation between maturity and color(value),biochemical changes and post-baking quality of tobacco leaves during flue-curing.Different maturity treatments were set up in Qiandongnan Prefecture,Guizhou Province,for Yunyun 87 central leaves to study the color values,biochemical changes and post-baking tobacco quality during flue-curing,and further analyze the correlation between maturity,color values and biochemical indexes during curing,as well as the correlation between maturity,post-curing grade quality and physical characteristics,chemical composition and color values.The results showed that:1.with the increase of maturity,the yellow degree of fresh tobacco leaf surface increases,the main and branch veins become white,the leaf tip gradually withered and down hooked,the leaf edge gradually inward curved,maturity spot from none to have,SPAD value decreases.2.During the flue-curing process of tobacco leaves at various maturity levels,the L value first increased and then decreased,the a value increased,the b and C values increased and decreased,and the H value decreased.As the maturity increases,the values of L,b,and C first increase and then decrease,the value of a increases,and the value of H decreases.The difference level is significant.The CIE LAB chromaticity coordinate map is used to trace the dots.By the end of color fixation,CM1 is light yellow,while CM2,and CM3 are close to orange;3.The lateral,longitudinal,and area shrinkage rates of tobacco leaves at various maturity levels showed an upward trend during the flue-curing process.With the increase of maturity,the lateral,longitudinal,and area shrinkage rates decreased from31.82%to 29.71%,16.39%to 13.07%,42.93%to 38.71%,respectively,from CM1-CM3,but the difference in lateral shrinkage rates was not significant.4.The moisture content,dry matter,and SPAD values of tobacco leaves at various maturity levels showed a downward trend during the flue-curing process;PPO、α-Amylase and protease showed a double peak trend of ascending-descending-ascending-descending;The content of total sugar,reducing sugar,and potassium gradually increased,while the content of starch,total nitrogen,and protein gradually decreased,while the content of nicotine first increased and then decreased.With the increase of maturity,the rate of decrease of moisture,dry matter and SPAD value gradually increased,the activity of PPO increased,the activity ofα-amylase and protease increased and then decreased,the increase of total sugar gradually increased,the increase of reducing sugar and K~+content showed a trend of increasing and then decreasing,the decrease of starch and protein increased and then decreased;the decrease of total nitrogen gradually increased,and there was no significant difference of nicotine.5.from the baking characteristics,with the increase of maturity,the ease of baking gradually increases,but the baking resistance gradually decreases,that is,CM1 easy to bake medium,good baking resistance,CM2,CM3 easy to bake good,medium baking resistance.6.With the increase of maturity,the quality of post-baking tobacco leaves all showed regular changes.1)Grade quality:the orange-yellow smoke rate,upper medium smoke rate,and average price showed a rising and then decreasing trend,with CM2 being the best,at 65.08%,91.59%,and 31.50 yuan/kg,respectively.2)Physical characteristics:softness and filler value rose and then decreased,with CM2being the best,at 34.90m N,4.62 g/cm3;tensile strength gradually increases,with CM3 being the best at 2.53N;thickness gradually decreases,with CM3 reaching a moderate level of 113.59um.3)Chemical composition:total nitrogen,protein and starch content gradually decrease,nicotine content first decreases and then increases,total sugar,reducing sugar,K~+,sugar-base ratio,potassium-chloride ratio,all first increase and then decrease,Cl-and two sugar ratios increase,with CM2 scoring the highest in the overall evaluation,at 99.55.4)Evaluation of smoking quality:aroma quality,eating flavor,stimulation,aroma volume score,total evaluation score increased and then decreased,with CM2 scoring the highest,miscellaneous gas score increased,CM3 scoring the highest.7.According to the comprehensive baking characteristics of different maturity tobacco leaves,CM2 was the best in terms of appearance quality,chemical composition,and smoking evaluation quality,followed by CM3,and CM1 was the worst.The appearance characteristics of CM2 during harvest are:comprehensive yellowing of 70%,main and branch veins turning white of about 2/3,leaf tips slightly withered and hooked down,leaf margins incurved,occasionally mature spots appearing,and SPAD values of about 19.3-20.3.8.Pearson correlation analysis showed that there was a strong correlation between color values and biochemical indicators during flue-curing process;There is a strong correlation between maturity and quality indicators of cured tobacco leaves;There is a strong correlation among grade quality,physical characteristics,chemical composition,and color value of flue-cured tobacco leaves.9.The stepwise regression equations were established using stepwise regression method to determine the color value of tobacco leaves with maturity and biochemical indexes during roasting,the physical characteristics indexes of tobacco leaves with chemical composition after roasting,and the grade quality of tobacco leaves with physical characteristics,chemical composition and color value after roasting with high confidence(R~2>75%),in which the color value of tobacco leaves during flue-curing was mainly affected by maturity,dry matter,moisture,PPO,total sugar,total nitrogen,nicotine,potassium and protein.The softness of tobacco leaves after roasting was affected by the two sugar ratios and total sugar;the tensile strength was affected by the Schmuck value and total sugar;the filling value was affected by the sugar to alkali ratio;and the thickness was affected by the Schmuck value and reducing sugar.Upper medium smoke rate was mainly affected by softness,nicotine,C value;green smoke rate was mainly affected by thickness,starch,a value;miscellaneous smoke rate was mainly affected by thickness,protein,potassium,a,L,C value;average price was mainly affected by filler value,total sugar,L value;orange yellow smoke rate was mainly affected by tensile strength,protein,a,L,C value;yellow smoke rate was mainly affected by tensile strength,protein,total sugar,a,L value.10.The BP neural network model constructed based on L value,a value,b value,C value,H value and SPAD value can achieve a more accurate judgment of fresh tobacco leaf maturity,and its higher reliability can provide a reference for future intelligent maturity harvesting.