Rresearch On Key Flavor Components Of Liupao Tea

Liupao tea,a historical famous dark tea product,originated from Guangxi province of China.It has unique flavor quality characteristics and health-care effects,which has attracted much attention in recent years.This thesis mainly focuses on the flavor of 24 loose Liupao tea samples.Quantitative descriptive analysis(QDA)and cluster analysis(CA)were used to analyzed the flavor characteristics of tea samples.High performance liquid chromatography(HPLC)and gas chromatograph-mass spectrometer(GC-MS)were used to analyze flavor components exist.Partial least squares regression(PLSR)and taste activity value(TAV)were used to analyze the relationship between taste components and taste characteristics.Gas chromatography-olfactometry(GC-O),odor activity value(OAV)and aroma character impact(ACI)were used to identify the key aroma components of different flavor type samples.The aroma recombination test was used to verify the key aroma components of aging fragrance in Liupao tea.The main findings were as follows:1.A 11-member sensory panel was established for the evaluation of Liupao tea after selection,training and assessment.The major sensory attributes of Liupao tea were bitter,astringent,sour,sweet,umami,mellow,aging,fungus,woody,rice straw,sweet-fruity and Chinese medicine-like.Valuation analysis of group consistency,panelists' discrimination ability and repeatability ability based on Panel Check software showed that the trained panel performed well and the data was reliable.According to the cluster analysis based on taste evaluation results of quantitative descriptive analysis,the24 tea samples were divided into 3 taste types,namely bitter type,strong mellow type and sweet-mellow type.According to the cluster analysis based on aroma evaluation results of quantitative descriptive analysis,the 24 tea samples were divided into 4 flavor types,namely Chinese medicine-like fragrance type,aging fragrance type,fungus fragrance type and sweet rice straw-like fragrance type.2.A total of 58 nonvolatile compounds were detected by HPLC.Among them,the compounds with higher average content mainly included theabrownin,caffeine,soluble sugar etc.Analysis of TAV indicated that the taste components that make an important contribution to taste quality mainly included GC,EC,EGCG,ECG,GCG,caffeine,gallic acid,Que-rut,Que-gal,oxalic acid,acetic acid,succinic acid,ascorbic acid,asparagine,aspartic acid etc.Analysis of PLSR-VIP indicated that there were 19,20,19,25,17 and 15 key taste components that affected bitter,astringent,sour,umami,sweet and mellow,respectively.A significant positive correlation was found between bitter intensity and the contents of ECG,GCG etc.A significant negative correlation was found between bitter intensity and the contents of soluble sugar,theabrownins etc.A significant positive correlation was found between astringent intensity and the contents of Myr-rha,Kae-rut etc.A significant negative correlation was found between astringent intensity and the contents of soluble sugar,theabrownins etc.A significant positive correlation was found between sour intensity and the contents of ascorbic acid,succinic acid etc.A significant negative correlation was found between sour intensity and the contents of GABA,threonine etc.A significant positive correlation was found between sweet intensity and the contents of soluble sugar,GABA etc.A significant negative correlation was found between sweet intensity and the contents of ECG,caffeine etc.A significant positive correlation was found between mellow intensity and the contents of soluble sugar,theabrownins etc.A significant negative correlation was found between mellow intensity and the contents of quinic acid,ECG etc.All the key taste components that affected umami did not reach significance on umami intensity.3.A total of 82 volatile components were detected by GC-MS,including 20 alcohols,17 aldehydes,13 ketones,11 esters,5 hydrocarbons,2 phenols and 13 nitrogenous heterocyclic compounds.Among them,the compounds with higher average content mainly included(E)-furan linalool oxide,(E)-pyran linalool oxide,(Z)-furan linalool oxide,dihydroactinidiolide,cedrol,etc.The active aroma compounds of 4flavor typical samples were identified by GC-O and OAV.The results showed that there were 12,22,17 and 19 common compounds that affected fungus fragrance,sweet rice straw-like fragrance,Chinese medicine-like fragrance and aging fragrance,respectively.1-Octen-3-ol,?-lonone and decanal were main aroma components in fungus fragrance tea samples,which also displayed the fragrance of fungus-like,green and floral.Phenethyl alcohol,dihydroactinidiolide and nerol were main aroma components in sweet rice straw-like fragrance tea samples,which also displayed the fragrance of sweet and flower.Methoxybenzenes,cedrol,nerolidol,?-ionone and 1-nonanal were main aroma components in aging fragrance tea samples,which also displayed the fragrance of aging,flower,fruit and woody.Aroma recombination based on the results of GC-O effectively verified the key aroma components of aging fragrance Liubao tea.