Effects Of Curing Methods On The Physiological And Biochemical Changes And The Quality Of Yellow Sun-cured Tobacco

Yellow sun-cured tobacco has been used the traditional sun-curing method in Jiaohe,Jilin,and lack of scientific and systematic specification of modulation system as a guide.Since this modulation,tobacco leaves often lack aroma,less oil,uneven color,and heavier green gas.In order to improve the quality of yellow sun-cured tobacco,the effects of the different modulation measures on the main substance during the curing process and the quality of the tobacco were studied.The main research results are as follows:1.In the process of modulation,the water content of leaf and main vein of tobacco leaves decreased gradually,the drying rate of tobacco in the greenhouse curing system was fastest,the conventional sun-cured method was followed,and the water content of the stacking tobacco leaves was higher.On the whole,water loss rate of tobacco leaves and veins with broken veins is faster.2.The amylase activity of tobacco leaves showed a downward trend during the sun-cured process,and showed a significant positive correlation with leaf water content.The enzyme activity of tobacco used tacking method was higher and maintained for a long time,especially for the stacking treatment(T3).The greenhouse drying system decreased sharply after the first 3d,and the conventional drying system dropped sharply at 9d.Activity of nitrate reductase increased initially and decreased finally in the whole curing process.Except for the conventional treatment reached its maximum in 3d,the other treatments were in 12 d and greater than that of the conventional treatment.The polyphenol oxidase increased first and then decreased,and the peak time of the treatment was different.T5(broke veins then sun-cured in greenhouse)was the earliest,T1(conventional method)and T6(s?n-c?red in greenhouse)were second,the other three treatments were the latest.3.In the curing process,the starch content of tobacco leaves was always decreasing,and the total s?gar and reducing sugar were increasing gradually.The speed of change is faster and slower.Starch degradation occ?rs mainly in the first 6d,and T2 degradation is the fastest.The total sugar and reducing sugar mainly increased in the first 9d.At the end of the modulation,the starch content of the stacking tobacco leaves was the lowest,and the sugar content was the highest.4.Total nitrogen content changed little.Soluble protein showed a downward trend,and T5 and T6 decreased the fastest,followed by T1 and T2,while T3 and T4 declined the slowest.The change trend of free amino acids was opposite to that of soluble protein,and increased with the modulation process.Nitrate content increased first and then decreased.The correlation analysis showed that the water content of tobacco leaves was significantly negatively correlated with free amino acids,and there was a significant positive correlation with soluble protein.It is worth noting that T1 and T5 have reached a very significant level.It is indicated that higher moisture content is not cond?cive to the degradation and transformation of soluble protein,and inhibits the accumulation of free amino acids.5.The pigments of tobacco leaves were decreasing during the modulation period,and the degradation was mainly in the early stage of curing.The stacking treatment was fully degraded,while the residue in the greenhouse was larger.The variation rule of polyphenols was inconsistent,the content of polyphenols of T6 was higher and T3 was lower.The carotenoids degradation,maillard reaction products and cembranoids degradation products all increased,the chlorophyll degradation products and aroma contents were increased first and then decreased,and phenylalanine degradation products reduced first and then increased.The content of aroma substance of T2 was relatively higher,and the greenhouse treatments had more loss.6.In the curing process,nicotine content decreased,while nitrite content increased gradually,and the rate of increase was fast,slow and fast.The content of NAT showed an increasing trend in the modulation period,while NAB had little change.The contents of NNN,NNK and TSNAs all first decreased and then increased.The content of TSNAs was the lowest in T3 treatment.7.The total nitrogen content of sun-cured tobacco leaves which treated by T3 and T4 was lower and the s?gar content was higher,b?t the average price was higher.However,T5 and T6 treatment had the highest residual amo?nt of starch and the total amount of aroma was the lowest.T3 showed the largest leaf length,leaf width and leaf area,but the stem ratio was highest.T2 was at the middle level of chemical composition,lowest stem ratio,highest neutral aroma content and highest score of evaluation score.In a comprehensive view,the contents of all substances varied moderately and appropriately of the yellow sun-cured tobacco which used conventional sun-curing after broking the veins of tobacco leaves,and the content is superior,the comprehensive performance of the tobacco leaves is also the best.For local area,this mod?lation method is the most s?itable.