| China has the largest area to grow tea in the world,which also has the long history of drinking tea and enormous people who are accustomed to drink tea.Higher and higher demands are proposed on the tea quality with the improvement of the living level and health consciousness. The type,the content and the ratio of the tea components are closely related to the tea quality.The fresh leaves from tea plant are directly in the process of making without washing-up.We usually drink the water which dip in the tea,but not to eat the tea-leaf. We should detect the tea components using the tea-water other than the tea-leaf.Recently,in order to make the detection more accurate,the national standard method using for detection is always changing.In this study determined several dark tea's tea polyphenols content,and use the GB/T8313-2002 method and GB/T8313-2008 method to determine the tea polyphenols of dark tea and other teas. Meanwhile,several tea polyphenols extracts were determined by liquid chromatography, to analyze the reasons of the differences of tea polyphenols content of these teas.Using GB/T8313-2002 method and GB/T8313-2008 method to determine the tea polyphenols content have obvious differences. Dark tea, except Qingzhuan tea and Fuzhuan tea, the result of tea polyphenols content determination which used GB/T8313-2002 method to determine are lower than that used GB/T8313-2008 method to determine,the other are higher than GB/T8313-2008 method, basically higher at 20%-40%.Determined the catechins of tea polyphenols extracts by HPLC, found out that the main composition of Qingzhuan tea and Fuzhuan tea's catechins is EGCG, each accounted for 58% and 46% Polyphenols or so.Fluoride is one of the necessary human elements.It can be imbursmented in human body,affect the body health.It should be necessary to detect the fluoride ratio of food accurately. In recent years,there are many methods to determine the fluoride at home and abroad.We determine fluoride of tea water by the use of fluoride ion-selective electrode.Soaking condition is also the influence factor in the determination of fluoride in tea water excpte the determination method.The purpose of this paper is to select the best way by comparision from some factors,for example;the composition of buffer solution,the reduction ratio,the time of soaking, the hydrochloric concentration in using,the temperature,the ratio of tea and water.The content of fluoride in the same tea is different using the distinct soaking condition when some factors are evident,the others are negelectful.The best soaking conditions are:the ground tea,the HCL concentration 0.10N 10ml,the ratio of tea and water 1g:50ml,the time one hour.Longjing tea is one of the traditional well-known tea in our country.It was produced in Song Dynasty,famous in the Yuan Dynasty,developed in the Ming Dynasty and boomed in the Qing Dynasty.It has a history of more than one thousand and two hundred years. After a glass of Long Jing tea is made, you should first look at its fresh green tea leaves in beautiful shape, then lift the glass to smell its aroma before enjoying its refreshing taste. Longjing tea is famous for its green color, delicate aroma, mellow taste and beautiful shapeLongjing tea in history may be divided into three kinds:Shi Feng Longjing,Mei Wu long jing and West Lake Long jing.In recent years,with the development of market economy,the need for the good green tea is increasing.Longjirig tea is brought flourishingly opportunity of survival.There are fifty cities to grow Longjing in Zhejiang province.The tea aroma is one of the important indexes for the tea quality.Many factors influence the tea aroma,for example,different tea,different producing area and so on.This is also true for Longjing.Now we detect six kinds of Longjing tea in order to compare their advantage and disadvantage.The meaning of this is to select the best producing process.
|
PDF Full Text Request