Study On The Influence Of Extraction Technology On The Quality Of Tea Extract

Tea is one of the most economic agricultural products in China.Tea extract is an important intermediate product of deep processing of tea.And investigating the influence of extraction technology on the quality tea extract will be benefit to the deep processing of tea.In this study,we investigated the influences of extraction technology on the catechins,caffeine,sensory indexes and volatiles of green tea extract.The main results were listed as follows:The process parameters of the powdery tea and the caffeine free tea were optimised by single factor experiment.And the optimal condition obtained with leaching temperature 90 oC,leaching time 60 min and ratio of water to tea 20:1.In addition,the optimal process parameters of the flake tea was obtained with leaching at 100 oC for 10 min,ratio of water to tea 80:1,and pH 5.5.Catechins,caffeine,theaflavins and thearubigins of the tea extract were detected.The results showed that the content of caffeine,theaflavins and thearubigins of the flake tea extract were 333.7 ?g/mL,0.2 mg/mL and 0.9 mg/mL,respectively,and that the content of catechins was little.The content of catechins,caffeine,theaflavins and thearubigins of the powdery tea extract were 2433.4 ?g/mL,1433.4 ?g/mL,2.2 mg/mL and 11.8 mg/mL,respectively.The content of catechins,caffeine,theaflavins and thearubigins of the caffeine free tea extract was 2337.4 ?g/mL,211.2 ?g/mL,1.3 mg/mL and 9.5 mg/mL.The flavor,color and aroma of tea extaract were analysised by sensory evaluation.The result showed that the flavor of flake tea extract was great,slightly bitter,the color was light yellow and bright,and aroma was fruity and grass incense.The flavor of powdery tea extract was weak,heavier bitter and astringent,the color was red and slightly cloudy,and the aroma was fruity and combination.The flavor of caffeine free tea extract was weak,heavier bitter and astringent,the c olor was red and slightly cloudy,and the aroma was fruity and combination.Furthermore,the volatiles of the tea extract were detected by GC-MS.6-Methyl-5-hepten-2-one,1-Octen-3-ol,hexanal and(E)-2-Heptenal were the main volatiles of the flake tea extract,and their concentration were 647.8,456.2,443.7 and 421.0 ?g/L,respectively.Linalool and nonanal were the main volatiles of the powdery tea extract,and their concentration were 360.0 and 316.1 ?g/L,respectively.Nonanal was the main volatiles of the caffeine free tea extract,and the concentrations was 243.8 ?g/L.Besides,?-Ionone and decanal were the characteristics flavoring composition of the flake tea extract,and ?-Ionone was the characteristics flavoring compositions of the powdery tea and the caffeine free tea extract.The total odour activity value of the flake tea extract was higher than that of the powdery tea extract and the caffeine free tea extract.But the total odour activity value of the caffeine free tea extract was approximately close to that of the powdery tea extract.This results indicated that tea extraction technology had the important influence on catechins,caffeine,theaflavins,thearubigins and volatiles of tea extract.The study will ba benefit to the further processing of tea.