The Fingerprint Analysis Of White Tea Color And Aroma

White tea,as the unique tea category to China,has unique color and aroma quality characteristics.And flavonols are the main color material of tea color,dry tea aroma and beverage aroma of white tea presenting differences for different picking tender degrees,producing area and varieties.It studied two parts of white tea color quality and aroma quality.First of all,using the method of orthogonal experiment to determine the measurement method of the main color compositions concluding flavonols of white tea,white tea was analyzed on the withering leaves flavonols' change rule and its relationship with color difference,and the relationship between flavonols and tea color quality of white tea was studied.Secondly,used the method of SPME-GCMS to analyze the aroma composition change of dry tea and beverage of white tea and the fragrances of baekho silver needle and white peony,at the same time,tested and analyzed the dry tea aroma quality of white tea by the electronic nose technology.The results of research on white tea color showed that:(1)Rutin,arbutus pigment,quercetin and kaempferol could be effectively separate under the HPLC separation conditions,and,higher precision and standard addition recovery rate were gained within their obtained linear scope of the standard curve equation.The optimal hydrolysis conditions for the flavonol substances ofwhite tea was followed:5 mL 3 mol·L-1 HCL was added to the 5 mL white tea extract,then hydrolysised 30 min in 80? water bath pot.It also showed that the precision of the optimal hydrolysis method was relatively high;the kaempferol in hydrolysis process was the most stable,while arbutus pigment was easy to be resolved;the hydrolysis conversion of rutin was 94.32%.It was concluded that the HPLC detection method and the optimal hydrolysis method were used to determine the flavonol substances content of white tea,which was feasible and could make the hydrolysis of the total flavonol glycosides in white tea extracts tend to be maximized.And in the withering processes of white tea,as the moisture content of withering leaves gradually reduced.the brightness(L*)and the yellow and blue degree(b*)of the Bai Mudan's withering leaves of Fuding dabai tea and Fuding dahao tea were falling,while the red and green degree(a*)were on the rise.The flavonol glycosides levels of Fuding dabai tea fell slightly on the whole,and Fuding dahao tea's flavonol glycosides rose slightly.The kaempferol glycosides of Fuding dabai tea and the brightness,red and green degree,and yellow and blue degree of withering leaves were in most dose relations,which showed that the kaempferol glycosides' influence on the withering leaf's color and luster was larger than arbutus pigment glycosides and quercetin glycosides.While the correlation between the flavonol glycosides and the withering leaf's color and luster was not significant.(2)The quercetin content and beverage brightness(L*)of Fuding baekho silver needle were significantly higher than that of Zhenghe baekho silver needle,the content of arbutus pigment,quercetin and beverage brightness(L*)of Fuding white peony which were significantly higher than that of Zhenghe white peony,the beverage chromaticity values(a*,b*)of Fuding white tea which were significantly less than Zhenghe white tea And the quercetin of baekho silver needle had significant effects on beverage chromaticity(a*),arbutus pigment of white peony having significant effects on beverage brightness(L*),arbutus pigment and kaempferol having very significant influences on beverage chromaticity(b*).And to classify the origin and variety of white tea samples based on the index of color,the results showed that producing area clustering effect and variety discrimination effect of white tea were in better levels,and the variety discriminants could correctly classify 95.3%of white tea samples.In addition,the color difference values(L*,a*,b*)were significantly associated with sensory evaluation of white tea color.As a result,color difference meter was used for the determination of beverage color,which could partly replace artificial sensory evaluation of color,reducing the fatigue of eyes for too long time tea review.The results of research on white tea aroma showed that:(1)There is some difference between baekho silver needle dry tea aroma and white peony dry tea aroma,and different regions of white tea aroma is different.Among them,the dry tea aroma components of baekho silver needle mainly classed terpene hydrocarbons,and terpene alcohols were the main aroma components of dry tea of white peony.3-carene was the characteristic aroma component of baekho silver needle dry tea of Fuding and Zhenghe areas,while linalool and its oxides were the characteristic aroma components of white peony dry tea of Fuding and Zhenghe areas.To classify the origin and variety of white tea samples based on the main fourteen kinds of aroma components of dry tea of white tea,the results showed that producing area clustering effect and variety discrimination effect of white tea were in better levels,and the variety discriminants could correctly classify 94.6%of white tea samples.(2)The types and concentration of beverage aroma components of Baekho silver needle and white peony were higher than that of dry tea.Among them,the beverage aroma components of baekho silver needle mainly classed hydrocarbons,while the terpene alcohols and terpene hydrocarbons were the main aroma components of white peony beverage.3-carene and beta-myrcene were the characteristic aroma components of baekho silver needle beverage of Fuding area,and 1,1-dimethyl-2-(3-methyl-1,3-butadiene)-cyclopropane and 3-careen were the characteristic aroma components of baekho silver needle beverage of Zhenghe area,while linalool and beta-myreene were the characteristic aroma components of white peony beverage of Fuding and Zhenghe areas.To classify the origin and variety of white tea samples based on the main fifteen kinds of aroma components of white tea beverage,the results showed that producing area clustering effect and variety discrimination effect of white tea were in better levels,and the variety discriminants could correctly classify 98.2%of white tea samples.(3)The aroma response values of electronic nose sensors were significantly correlated with sensory evaluation of white tea aroma,and the sensors could be well response for the main aroma components of white tea.To classify the origin and variety of white tea samples based on the aroma response values of electronic nose sensors,the results showed that producing area clustering effect and variety discrimination effect of white tea were in better levels,and the variety discriminants could correctly classify 96.4%of white tea samples.Therefore,the electronic nose technology could well classify the white tea of origin and variety,and to a certent extent,it could make up the subjective limitation of human sensory evalution.