Studies On Chemical Constituents Of Oolong Tea Quality Based On The International Standard

In this paper,the Fujian and Guangdong Oolong tea were selected as test materials to systematically analyze 14 chemical components,which include the water?water extract?total ash?crude fibre?total soluble sugar?total polyphenols?total catechins?caffine?total free amino acid and components?minerals?aromatic substances?tea soup colour and PH of Oolong tea,using factor analysis,cluster analysis and discriminant analysis,according to the principle of priority of international standards,using the appropriate standards of international and national inspection standard,to provide a reference for The International Standard Oolong tea,and to look for the quantitative factors of quality evaluation and product identification,and establish evaluation and discriminant function.The results show that:(1)For the different area,variety,grade and type,there are different degrees of difference and correlation between the kind?content and ratio of the main chemical constituents in Oolong tea.The content of phytol,nerolidol,linalool and its oxidation-reduction products are more higher in the all aromas,the three aroma compounds and Green value exist significant differences between areas and varieties.There are significant differences between areas,varieties and themselves in the major flavor of free amino acids,but years not.Many free amino acids components,special The,are highly correlated.The major of Oolong tea soup colour and PH indicators are significant difference in different brewing times?areas and varieties,but in the temperature range of sensory assessment and at different grades are not.(2)Derived five factors which reflectf the fresh?sweet?thick and strong taste,aromas,maturity of leaves by factor analysis,and the corresponding quality assessment function were established and determined.The discriminant analysis by 3 classes independents which are five quality factors,main chemical constituents,tea soup colour?PH and the main free amino acid components showed that the grades correct identification of five quality discriminating factor was lower to 56%,but the areas and varieties correct identification were higher to 92%and 96%;the discriminant function by main chemical constituents discriminating factor have a higher discriminant level(100%)on areas?varieties and grades of the Oolong tea;soup colour discriminating factor have the high rate of correct identification on areas(97%),but varieties and grades wre lower(less than 80%);For the type?grades and manufacturers of the same product,the rate of correct identificationof the discriminant functions which established by chemical constituents,were all about 100%.(3)The comparison of three kinds of tea based on the above analysis,water?total ash?total free amino acid?caffine?AA/C?water extract and Ca are the important of quality evaluation and product identification factor.Compared with the polyphenols or catechins chemical composition,AA/TP and AA/C are more advantages on the aspects of Oolong tea evaluation and discriminant.