Control Of Bitter Taste In Ready-to-Drink Tea

Ready-to-drink green tea is a canned or bottled beverage which contains tea functional components and has a typical green tea flavor.It can be prepared by using dilute or concentrated green extract or instant green tea.Generally,green tea has a bitter taste because the major tea components in green tea are tea polyphenols which have bitter and astringent tastes.Of course,the bitter taste is supplemented by an umami taste from amino acids.Bitterness and astringency are dominant taste in green tea.However,over bitterness of the taste is not accepted by consumers.It is necessary to control the bitterness during ready-to-drink tea processing in order to meet sensory acceptance of consumers.Although flavonoids level is lower than catechins in green tea,the taste threshold concentration of flavonoids is much lower than tea catechins.Flavonoids might be more important bitter taste components than catechins in green tea.The relationship of tea flavonoids to bitterness in green tea were studied in this study. Firstly,methods for extraction and HPLC determination of tea flavonoids were investigated.Secondly,the relationship of tea flavonoids to bitterness was established.Thirdly,molecular embedding was applied to control the bitterness in green tea.1.HPLC analysis of quercetin dehydrate,myricetin,kaempferol, quercetin-3-β-D-glucoside,quercetin-3-D-galactoside,vitexin-2"-O-rhamnoside, quercitrin hydrate,vitexin,isovitexin and rutin hydrate was studied.The optimum chromatographic conditions were as followings:the HPLC system consisted of shimadze LC-20AT with a four pumps gradient system(shimadze Co.Ltd.,Kyoto, Japan),a shimadze CLC-ODS column 0.15 m×6.0φ(shimadze Co.Ltd.,Kyoto, Japan).The flow-rate of the mobile phase was 1 ml/min.The column temperature was 35℃and sensitivity was 0.01 aufs.Linear gradient elution was used by two mobile phases.Mobile phase A consisted of acetonnitrile,acetic acid and water (3:0.5:96.5)and molie phase B consisted of acetonnitrile,acetic acid and water (50:0.5:49.5).The gradient elution was started at 72.5%(v)solvent A and 27.5%(v) solvent B.During the early 24 min,the solvent B was increased from 27.5%(v)to 45%(v),and then from 45%(v)to 80%(v)from 24 min to 29 min.Finally,the solvent B was maintained at 80%(v)till 45 min.2.Effects of different extraction methods on extractability of tea flavonoids were investigated.It showed that ethanol concentration,liquid/solid ratio,extraction temperature and duration had significant effects on flavonoids level in tea extracts. The optimum extraction conditions were confirmed to be 30%ethanol solution, extraction temperature 80℃,extraction time 3h and solid/liquid ratio 1:30.3.Relationship of chemical constituents to bitter taste of extracts of Chrysanthemum Morifolium Ramat flower and steaming green tea leaves was studied.It showed that levels of flavonoids and their glycosides were significantly and positively correlated to bitterness of the extracts.4.Molecular embedding withβ-cyclodextrin was applied to control the bitterness of tea solutions.It showed thatβ-cyclodextrin had a significant effect on the taste of bitterness of green tea.Whenβ-cyclodextrin was applied at levels between 0.4%and 0.6%,the intensity of bitterness was decreased significantly. However,the detectable levels of catechins,caffeine and flavonoids were not affected by the application ofβ-cyclodextrin.