Effects Of Air-curing Humidity On Physiology And Quality Of Cigar Tobacco Leaves

The quality of cigars is affected by the genetic characteristics of varieties,field cultivation,air curing and other factors,among which the air-curing process is the key link of cigar production,and the air-curing humidity has an important influence on the formation of high-quality tobacco leaves.In this study,cigar were grown and air-cured in Cuiba Air-cured Tobacco Test Base of Hubei Academy of tobacco sciences.Taking the cigar “Chuxue 10” as the material,the effect of natural airing(without airing room humidity)on the appearance quality of eggplant tobacco was analyzed by using liquid chromatography tandem mass spectrometry(LC-MS / MS)non targeted metabolomics technology.Taking the variety of cigar “Chuxue 14” as the experimental material,three kinds of drying humidity treatments of high humidity,medium humidity and low humidity were set up to analyze the changes of chemical components and related enzyme activities of tobacco leaves under different drying humidity.At the same time,metabonomics Technology was used to analyze the metabolic changes between different humidity treatments before and after the drying and to explore the effects of different drying humidity on the physiology and quality of cigar tobacco leaves during the drying period.In order to provide theoretical and technical support for the airing production of high-quality cigar tobacco in Cuiba area,the main results are as follows:1.Effects of natural air-curing on appearance quality and metabolism of cigar leaves.In the process of natural air curing,there are green spots of different sizes(referred to as “green spots”)on tobacco leaves,which seriously affect the appearance quality of tobacco leaves.The metabolomics was used to analyze the metabolome differences between “green spot” and normal tissue parts of tobacco leaves.The results showed that the contents of chlorophyll and chlorogenic acid in the“green spot” part are significantly higher than those in the normal part.The chlorophyll degradation of tobacco leaves is incomplete during the drying process,a large amount of chlorogenic acid is not oxidized into dark pigment,and the deposition of residual chlorophyll and chlorogenic acid at the end of the drying period is the cause of the “green spot” of air cured tobacco leaves.Chlorogenic acid and dihydrozeatin can be used as chemical markers in the formation process of “green spots”.Monitoring the content changes of them during the discoloration period of cigar curing can be used as one of the effective means to predict whether the leaves will produce “green spots”.There were significant differences in tyrosine metabolism,phenylalanine metabolism and flavonoid biosynthesis between the two parts.The humidity of the drying room in the yellowing period of tobacco leaves is low and fluctuates greatly,which may be the external environmental factor for the formation of “green spots”.It is suggested to use the humidity controlled drying room and appropriately increase the humidity in the yellowing period.2.Effects of different humidity treatments on physiology changes of cigar leaves during air-curing.During the drying process,the total water and free water contents of cigar leaves under the high humidity(T1),medium humidity(T2)and low humidity(T3)treatments continued to decrease.The water content decreased from 83.86% at the initial drying to 34.70%,26.68% and 20.31%,respectively.The free water content was completely lost on the 13 th,15th and 18 th days of drying,respectively.During the drying process,the total nitrogen content of tobacco leaves increased slightly,the nitrate nitrogen content gradually decreased,the potassium content gradually increased,and the chlorine content continued to decrease.The total protein showed a “slow-fast-slow” downward trend.The protein was significantly degraded from 6 to 24 days after air drying.The change of T1 treatment was the most intense,followed by T2,and T3 was the slowest.The amino acid content increased first and then decreased.The peaks of T1,T2 and T3 treatment appeared on the 12 th,18th and 30 th day of airing,respectively.The changes of total sugar and reducing sugar content are consistent,showing a gradual decrease,with T1 changing the most violently,T3 followed,and T2 changing the most gently.The changes of chlorophyll and carotenoid contents were the same,which decreased significantly 12 days before airing,and then remained basically unchanged.Amylase and polyphenol oxidase showed a“single peak” change,reaching the peak on the 6th and 24 th day of air drying,respectively.The content of MDA increased sharply within 0-12 days of drying,and then maintained a slow upward trend.3.Effects of different drying humidity on the quality of cigar leaves.At the end of air curing,the total sugar content of tobacco leaves under medium humidity(T2)treatment was significantly higher than that under high humidity(T1)and low humidity(T3),72.6%and 47.4% higher respectively.The content of reducing sugar was the highest,which was 2.00 times and 1.62 times higher than that of high humidity and low humidity air drying,which was more conducive to improve the color and elasticity of tobacco leaves and neutralize the alkalinity of flue gas.The contents of nitrate nitrogen and nicotine in medium humidity treatment were significantly lower than those in high humidity and low humidity treatment,and the safety of cigar smoking was higher.The chlorine content of medium wet air cured tobacco leaves was the lowest,potassium chlorine ratio was the highest,and the flammability was better than that of high humidity and low humidity treatments.Although there is no significant difference in starch content between medium wet air cured tobacco and other treatments,the content is the lowest,and the suction taste may be better.The sensory quality score of medium wet air cured tobacco leaves is the highest,which is mainly reflected in higher sweetness and better flammability.In conclusion,the medium wet air treatment(withering period 85%,discoloration period 80%,color fixing period 75%,dry gluten period 55%)had a good effect on the formation of good quality of cigar tobacco.4 Effects of different drying humidity on the metabolome of cigar leaves.A total of 424 metabolites were identified before and after airing,including 327 up-regulated metabolites,97 down regulated metabolites and 19 significantly different metabolites.Compared with the initial airing,the up-regulated metabolites of cigar leaves after airing are mainly amino acids and their analogues and carbohydrates,epsilon-(gamma-Glutamyl)-lysine and tryptophyl-leucine changed significantly before and after airing,and carotenoid biosynthesis pathway was a significant enrichment metabolic pathway.At the end of airing,the metabolites of amino acids and carbohydrates(3monosaccharides and 1 oligosaccharide)in medium humidity airing cigar leaves were significantly higher than those in high humidity and low humidity airing.Tryptophyl-leucine and N1-(α-D-ribosyl)-5,6-dimethyl-benzimidazole may be related to the quality of medium wet air cured tobacco leaves.Galactose metabolism,ABC transporter and fructose and mannose metabolism are significant enrichment pathways.