Study On The Relationship Between Appearance And Internal Quality Of Tobacco Leaves During Curing

In order to clarify the relationship between appearance and internal quality of tobacco leaves during the process of tobacco baking in intensive curing room.The NC102 was used to conducts the change rules of leaf appearance color parameters,leaf shrinkage,leaf tissue structure,internal moisture content,pigment,main chemical components,aroma components and PPO activity under different baking conditions.And further analysis of the relationship between appearance index and internal quality.The main results were as follows.1.Changes of appearance of tobacco leaves during curingThe results showed that the changes of color parameters under different curing conditions exhibited commonality: L value and b value showed an upward-stable-downward trend,and a value increased rapidly in the early stage of baking.The L value and b value of tobacco leaf increased with the temperature during pre-yellowing.During the early stage of the color fixing,the L value and a value of tobacco leaf increased with the heating rate.Under the condition of variable frequency fan(30?50Hz),L value of tobacco leaves increased,a value and b value decreased.The blade shrinkage rate increased during the baking process,and the area shrinkage rate >transverse shrinkage rate > longitudinal shrinkage rate.There was no significant difference in the shrinkage of tobacco leaves at different temperatures pre-yellowing.The slower of heating rate in the early stage of fixation,the higher of fixation temperature,each shrinkage rate increased under the frequency conversion fan.The changes of leaf tissue thickness before and after curing were as follows: spongy tissue >palisade tissue > upper epidermis > lower epidermis.The palisade tissue and spongy tissue were thinner with the higher of temperature at yellowing stage.The thickness of lower palisade tissue,sponge tissue,upper epidermis and blade of variable frequency(30?50Hz)fan were less than that of constant frequency fan.2.Changes of internal quality of tobacco leaves during curingThe amount of chlorophyll degradation was increased with the higher temperature in the early stage of yellowing.The higher of heating rate,the lower the moisture content and the higher the carotenoid degradation were during the early stage of color fixing.The water loss rate was increased with the higher of color fixing temperature in the fixed color period.Under the frequency conversion fan(30?50Hz),the water loss in the fixed color period of tobacco leaves was more stable,and the degradation amount of carotenoids was lower.After curing,the starch content decreased from 25%?27% to less than 5%,and the total sugar and reducing sugar content increased from 5%-8% to 15%?22%.Higher pre-yellowing temperature,slower pre-fixing heating rate,higher fixing temperature and variable frequency fan curing conditions can improve starch degradation and increase the content of total sugar and reducing sugar.The total amount of aroma components reached the peak at 42?47?,and the content of phenylalanine increased with the higher temperature in the early stage of yellowing.In the early stage of color fixing,the carotenoid degradation products were increased with the heating rate,and the cypranoids decreased.With the increase of color fixing temperature,the contents of chlorophyll degradation products and phenylalanine increased,while the contents of Maillard reaction products,cederanes and other aroma compounds decreased.Under the condition of variable frequency fan(30?50Hz),the content of aroma components in the early and middle stages of baking was lower than that of constant frequency fan,and the difference was small at the end of curing.The peak of PPO activity in middle leaves appeared at about 45 ?,and it was almost inactivated in dry gluten stage.The PPO activity of upper leaves was higher in the stage of fresh tobacco and yellowing.The activity of PPO increased with the higher of temperature in the early yellowing stage.The faster of heating rate and the higher the fixing temperature,the higher the PPO activity was.Under the condition of variable frequency fan,the PPO peak activity of tobacco leaves was lower.3.The correlation between the appearance and the inside of tobacco leaves during curingPearson correlation analysis and stepwise regression analysis showed that the appearance color parameters,shrinkage and tissue structure were significantly correlated with the content of moisture,pigment,starch and some aroma components in tobacco leaves during curing.The regression equation of appearance indexes and some internal indexes had a high degree of fit.