Study On Flavor Quality Of White Tea Based On Sensory Evaluation And Chemometrics

In this thesis,sensory evaluation and chemical components were combined to study the flavor quality of different varieties of white tea,different tenderness,taste 6and aroma of different parts,and explore the chemical composition of taste and aroma properties.The main conclusions are as follows:The sensory quality of white tea taste was defined as "clear,fresh,sweet,mellow,strong and thick".The taste properties of 13 varieties were different.“Clear,fresh,sweet,mellow,strong are the main flavor attribute of white tea."Clear" is the common taste attribute of Fujian,Zhejiang and Hunan varieties of white tea,while the taste of Yunnan and Guangxi varieties of white tea is mainly "sweet,mellow and thick".The three taste properties of clear,fresh and mellow were positively correlated with the contents of amino acids,flavonol glycosides and the ratio of amino acids to alkaloids and catechins,while the contents of caffeine,alkaloids and gallic acid were negatively correlated with the three taste properties.Theine,alkaloid total,catechin total,EGCG,galloylated catechins and other components are the key factors of flavor concentration(convergence)of white tea.The sensory quality of white tea aroma was defined as "fragrance,sweetness,honey and flower" 4 attributes.9 varieties of white tea aroma attributes were different.Under the conditions of this experiment,the aroma of white tea was mainly composed of alcohols(63.64%),aldehydes(13.09%)and ketones(9.42%).The aroma amounts and types of Meizhan and Chunyu 2 with the characteristics of "floral fragrance" were the highest among the 9 varieties.?-octyl lactone and citronella aldehyde are the characteristic substances of clear fragrance.Geraniol,2-furfuryl alcohol and 2-hexenaldehyde are the key substances of sweet fragrance,and 2-hexenaldehyde is the characteristic substance that distinguishes sweet fragrance from honey fragrance.The content of geraniol was the highest and higher than that of linalool and its oxides.In addition to linalool and its oxides,phenyl alcohol,phytal ketone,terephthalol,terephthalone,hexanolactone,indoles,cyclopentanol,benzaldehyde,cis-octanol,2-methyl-butyraldehyde,methylheptenone,2-pentanone,cis-3-hexenolbenzoate,4-methyl-3-pentanol,etc.contributed a lot to the formation of white tea flowers.With the decrease of tenderness level,the "clear" and "fresh" properties of white tea taste decreased,and the "rough" feeling increased.The total amount of gallic acid,theine,alkaloid,ester catechin and amino acid components decreased,while the components of non-ester catechin and flavonoids increased.With the decrease of the degree of tenderness,the "fresh" and "sweet" properties of white tea aroma quality decreased,and the "sweet" properties increased,and even the "coarse" smell was produced.The species of white peony is the highest in the four grades;Aldehydes are the highest in the aroma of pekoe,and mellow are the highest in other grades.In the four grades of white tea,alcohols,terpenes,lactones,and components such as linalool oxide,dihydroactactone,?-cyclocitral increased with the decrease of tenderness,while aldehydes,ketones and esters decreased first and then increased.The "raw" taste in aroma is related to hexanaldehyde;"Milli incense" is related to ?-terephthalol;"sweet fragrance" is related to 2-methyl-butyraldehyde."crude" is associated with 6-methyl-2-heptanone.There is a big difference in taste between tea pubescence and tea body without pubescence in sensory evaluation,but the chemical substances are basically the same.The content of flavones in pubescence was significantly lower than that in tea body,and the proportion of umami amino acids in total amino acids of pubescence was higher.Except Jinggu Dabai,the total amount of catechins,alkaloids and amino acids in white tea pubescence was lower than that in tea body.The obvious convergence of fish leaf taste is related to the high content of catechins,especially ester catechins.The aroma of acid substances in the fish leaf is significantly higher than other samples.Waxy leaves taste sweet and,except the flavone group other substances are lower;The aroma substances of non-terpene alcohols,ketones,esters,alkanes,hydrocarbons and lactones were significantly higher than other samples.