Analysis Of Free Amino Acids And Main Chemical Components In Tobacco Leaves During Maturity,Curing And Aging Process

Tobacco leaves Yunyan 87 were used as material,and continuous flow analyzer and high performance liquid chromatography(HPLC)were used as analyzing methods to study the dynamic variation of the content of free amino acids and main chemical components during maturity,curing and aging process,to provide theoretical and experimental guidance for revealing the corresponding relationship between leaf appearance,inner quality and aroma character with chemical components.The main results were as follows:(1)The content of plastid pigment decline greater after topping 21 day for middle leaves and 50 day for upper leaves.The content of reducing sugar was firstly declining then rising after topping 28 day for middle leaves and 50 day for upper leaves.The content of total free amino acid was firstly declining after topping 14 day for middle leaves and 10 day for upper leaves,then it came to balance.The results of correlation analysis showed that during maturity stage there was significant positive correlation between the content changing of plastid pigment and total free amino acid which were nitrogenous compounds.However,there was extremely significant negative correlation between the content changing of carotenoid and reducing sugar which were carbon compounds.(2)A high performance liquid chromatography(HPLC)method for determining 21 free amino acids in tobacco was optimized in experiment condition and parameters.80% ethanol15 m L was determined as solvent and vibrating for 1h,which had the best extraction efficiency.A good separation and detection of 21 amino acids was achieved.The recoveries ranged from 98.00% to 111.81%,relative standard deviation was less than 3%,detection limits ranged from 0.001 to 0.04 ug/mL.The linear correlation coefficients were above 0.99 in all cases.Thus,this method could be applied to analyze the content of free amino acid in tobacco leaves.The content of Proline,alanine,asparaginic acid,histidine and serine was high in tobacco leaves during maturity stage,and the content of these amino acids declined and finally became stable after 21 days of topping.(3)The declining rate of chlorophyll was obviously faster than carotenoids.The contents of reducing sugar and amino acids increased greatly during yellowing stage.Thecontent of free amino acids became stable after 45?,and the content of reducing sugar became stable after 50?,which indicated that it was quite important to control the rate and amount of water loss in different temperature stage during curing process,to diminish greenish leaves and lower the content of starch and protein in tobacco leaves,and improve the quality of tobacco leaves.(4)Research showed that,amino acids whose content declined in color fixing period were mainly asparaginic acid,histidine,alanine,asparagine,glutamate,cysteine and threonine,other amino acids like ptoline,arginine,phenylalanine,glycine and lysine also had a slight decline in content.Under the circumstance of cell death and respiration halt,the content of amino acids still declined,which indicated that some amino acids composition had participated in the non-enzymatic Maillard reaction,and generated Maillard reaction products with tobacco aroma.(5)Results of the variation of amino acids contents analysis during aging process showed that: The contents of amino acids in tobacco strips firstly went up then dropped during aging process,and reached the highest after 12 months of aging,then declined.Amino acids whose content went up after 12 months of aging were mainly proline,asparaginic acid,asparagine,serine,glutamic acid,cysteine,threonine and hydroxyproline,and most amino acids contents dropped as the aging process went.Several kinds of amino acids contents can no more be detected.While the proline contents of different producing areas continuously went up during aging,which indicated that most amino acids,except proline,that degraded from cell wall structural protein by microorganism could be absorbed in and utilized.(6)Correlation analysis results of main chemical components and sensory evaluation indice of flue-cured tobacco in different flavor type showed that:The content of reducing sugar in each leaf position of clear flavor and middle flavor type tobacco leaves was extremely significantly higher than those of strong flavor type.The content of nicotine in each leaf position of strong flavor type tobacco was significantly higher than those of clear flavor and middle flavor type.Both of the content of rutin in C3 F and X2 F leaves and the content of proline in B2 F leaves of clear flavor and middle flavor type tobacco was higher than tobacco of strong flavor type.Results of correlation analysis indicated that,the increasing content of reducing sugar,proline and rutin helped improve the aroma quality,amount of aroma,degree of smooth and the sense of mellow.For tobacco of clear flavor andstrong flavor type,Too high or low contents of nicotine would result in bad influence on sensory evaluation.