Effects Of Environmental Humidity On Drying Characteristics And Metabolic Mechanism Of Cigar Wrapper

Cigar is a kind of tobacco products with high value,with characteristics such as rich smoke,strong strength and delicate branches.With the rising of Chinese cigar this topic,industry demand for high-quality raw materials has been boosted,which promotes the development of cigar agriculture.Tobacco curing is the key period for the formation of the appearance quality and property of high-quality cigar wrapper,and environmental humidity is the main factor.It is of great significance to clarify the influence of environmental humidity on drying characteristics and metabolic network of cigar wrapper in the process of modulation.In this paper,we investigated the water loss and drying characteristics of tobacco leaves under different humidity in the modulation process through a split-zone test,with environmental humidity as the main zone and wrapper variety as the secondary zone.In addition,CX-010 was used as the experiment material,and the relatively high,medium and low humidity treatments were set in different drying periods to explore the antioxidant system as well as substance transformation of cigar wrapper under different humidity stress.Combined with non-targeted metabolomics,the effects of environmental humidity on the differential accumulated metabolites and metabolic pathways of tobacco leaves after aircuring and fermentation were clarified.The results showed that:1.The leaf and vein water loss in the drying stage of cigar wrapper have a sequence of connection.The bound water increased slightly when the free water loss rate is the highest.Humidity treatment has no effect on leaf thickness and accumulated dry matter,and only has an effect on leaf deformation during drying.Different kinds of cigar varied greatly in the modulation stage.The leaf water holding capacity of CX-007 is the worst,and the drying period of CX-012 is the longest.The water loss rate of the middle leaf is lower than the upper leaf.It is found that three parameters model of middle leaf and the page model of upper leaf are well described during the leaf drying process.2.The analysis of the critical period,short-term,of material transformation under the modulation stage humidity treatment indicated that medium humidity treatment promoted the activities of enzymatic antioxidants,such as POD,CAT,POD,PPOand inhibited the accumulation of non-enzymatic antioxidants(polyphenols)and malondialdehyde(MDA).It could reduce the oxidative damage of tobacco leaves,delayed the process of plasma membrane peroxidation and promoted the full transformation of substances.High humidity delayed the decomposition of chlorophyll and promoted the accumulation of TSNA.Low humidity promoted the decomposition of plastid pigment.3.Non-targeted metabolomics findings during the modulation phase(long-term):There were significant differences between high humidity,medium humidity and low humidity metabolism.A total of 63 differential metabolites were screened,including carbohydrates,organic acid,lipids,alcohols and polyols.Humidity regulated the transformation of polysaccharides to oligosaccharides and promoted the accumulation of osmotic regulatory substances(soluble sugars)by affecting the metabolism of galactose,ascorbic and aldarate metabolism.Through alanine,aspartate and glutamate metabolism,glycine,serine,threonine metabolism and lysine metabolism regulated the accumulation of non-enzyme antioxidants in tobacco leaves,such as quinic acid,proline,tryptophan,salicylic acid,shikimic acid.4.Non-targeted metabolomics at the fermentation stage showed that 55 different metabolites were screened,including amino acids and their derivatives,lipids and lipid molecules,benzenes and nucleotide metabolites.Humidity affected phenol,quinic acid,benzoic acid,shikimic acid,hydroxybenzoic acid and dihydroxybenzoic acid by regulating the degradation of aromatic compounds and metabolism of tyrosine,meanwhile promoted the brown deepening and accumulation of aroma substances in tobacco leaves under high humidity.Humidity could regulate the metabolism of aspartic acid,affected the accumulation of nicotinic acid(VB3),pantothenic acid(VB5),retinol(VA)and amino acids.It could affect the metabolism of fatty acids,such as palmitic acid,octanediic acid,arachidonic acid,promoted the acid-base balance and accumulation of aroma substances in tobacco leavesIn conclusion,the characteristics of cigar cultivars at the modulation stage are significant,and the appropriate modulation humidity should be selected according to different varieties.The humidity treatment at the modulation stage mainly regulates substance transformation and resistance to adversity stress by affecting carbon,nitrogen metabolism and antioxidant system of leaves.In the fermentation stage,the acid-base balance of cigar wrapper is regulated by affecting the metabolism of amino acids.Humidity promotes the formation of black polymers and accumulation of aroma by affecting the degradation of aromatic compounds and the metabolism of fatty acids.