Effect Of Curing Processes On The Physiology And Quality Of Upper Leaves Of Flue-cured Tobacco

The upper leaves of flue-cured tobacco are important raw materials for high-end cigarette formulations,but they are often unable to meet the quality requirements of the cigarette industry during production due to their tight structure,difficulty in dehydration and yellowing during curing,and insufficient conversion of their contents.Tobacco leaf curing is a key link in determining the quality and industrial usability of tobacco leaves.Exploring the changes in tobacco leaf substances during the curing process can provide reference for improving the overall quality of tobacco leaves.In order to improve the usability of the upper leaves of flue-cured tobacco,this study used Yunyan 87 as the experimental material and conducted a temperature controlled curing experiment during the dry gluten period in Lingbao Tobacco District,Sanmenxia City in 2020.Three treatments were set up,namely CK(the highest dry bulb temperature during the dry gluten period of 68 ℃),T1(the highest dry bulb temperature during the dry gluten period of 72 ℃),and T2(the highest dry bulb temperature during the dry gluten period of 75 ℃),to explore the impact of dry bulb temperature during the dry gluten period on the quality of cured tobacco leaves;This study used Yunyan 97 as the experimental material and conducted a sine frequency conversion curing test with a fan during the color fixing period in Yongde Tobacco District,Lincang City in 2021.Three treatments were set up,namely T1(fan frequency during the color fixing period is 20Hz)and T2(fan frequency during the color fixing period is sinusoidal frequency conversion,with a frequency range of 17-23 Hz and a period of 4h)T3(Sinusoidal frequency conversion of the fan during the color fixing period,with a frequency range of 18-22 Hz and a cycle of 2h)investigated the effects of fan sine frequency conversion technology on the physiology and quality of the upper leaves of flue-cured tobacco.The main research findings are as follows:1.During the fixed color period,the sine frequency conversion of the fan can improve the coordination of moisture loss changes in tobacco leaves during the curing process.Compared with T1 treatment,T2 and T3 treatments have more coordinated water loss and yellowing characteristics.Specifically,T2 and T3 treatments have significantly faster water loss rates in lower tobacco leaves compared to T1 treatment,and the moisture content of tobacco leaves is significantly reduced compared to T1 treatment;Chlorophyll a during the fixation period.The difference in chlorophyll b content among different treatments was not significant,and the degree of decrease in carotenoid content and degradation rate showed T1>T2>T3.At the same time,the regression analysis between the moisture content of tobacco leaves and plastid pigments showed that the results were consistent with the quadratic function model,and the model fitting degree was high.2.During the fixed color period,the sine frequency conversion of the fan can improve the osmotic regulation and antioxidant capacity of tobacco leaves during the curing process,and the degree of membrane lipid peroxidation of tobacco leaves is reduced.T2 and T3 treatments can significantly reduce the production of malondialdehyde(MDA),the accumulation rate of MDA content in tobacco leaves is slow,the content of MDA is significantly reduced compared with T1 treatment,and the three antioxidant enzymes of antioxidant enzyme defense system: superoxide dismutase(SOD),catalase(CAT),peroxidase(POD)activities are significantly increased compared with T1 treatment.3.The sine frequency conversion technology of the fan during the fixed color period can reduce the intensity of enzymatic browning reaction in tobacco leaves during the curing process.T2 and T3 treatments can significantly reduce the activity of polyphenol oxidase(PPO),which is significantly lower than T1 treatment.The polyphenol content in cured tobacco leaves is significantly increased,among which the content of chlorogenic acid,rutin,and neochlorogenic acid in cured tobacco leaves is T3>T2>T1.The content of cryptochlorogenic acid in cured tobacco leaves is T2>T3>T1,and the content of scopolamine in cured tobacco leaves is the highest in T1 treatment,with no significant difference between different treatments.4.The sine frequency conversion technology of the fan during the fixed color period can effectively improve the quality of tobacco leaves.T2 and T3 treatments can significantly promote the Maillard reaction process of tobacco leaves,and the amino acid content of flue-cured tobacco leaves is significantly increased compared with T1 treatment,and the six amino acids with higher Maillard reaction response are significantly increased,and the six amino acids are significantly positively correlated with the corresponding Amadori compound content of flue-cured tobacco.The overall content of Amadori compounds in flue-cured tobacco among different treatments showed the highest Fru Pro content and the lowest Fru Ile content.T2 and T3 treatments can significantly improve the quality indicators of cured tobacco leaves.The appearance quality of cured tobacco leaves is better,the chemical composition is more coordinated,and the content of neutral aroma substances is higher.The sensory quality evaluation of tobacco leaves is higher.5.Properly increasing the temperature during the dry gluten period can significantly improve the quality of cured tobacco leaves.Compared to CK treatment,both T1 and T2 treatments can shorten the dry gluten period curing time,reduce the curing energy cost by 0.66 yuan/kg and 0.56 yuan/kg,respectively,and promote a more coordinated internal chemical composition of the cured tobacco leaves.The content of neutral aroma compounds and petroleum ether extracts in the tobacco leaves has increased,and the aroma quality and quantity of single material tobacco leaves have been improved.However,as the temperature continues to increase,the degree of improvement in the quality of the upper leaves shows a weakening trend.In summary,the sine frequency conversion technology of the fan during the fixed color period can enhance the antioxidant capacity of tobacco leaves during the curing process and improve the quality of cured tobacco leaves.Compared to T3 treatment,the improvement effect is better;The temperature control technology during the dry gluten period can effectively shorten the curing time,reduce the curing energy consumption cost,and improve the yield and quality of the upper leaves after curing.Among them,T2 treatment has the best improvement effect.