| White tea is one of Chinese six traditional tea brands, which mainly produced in Fujian province. The techniques of making white tea is simple, it includes only two steps as withering and drying. Long-time withering is the characteristic of making white tea, during which a series of complex physical and chemical reaction happened while withering leaves are losing moisture. Based on these reactions, white tea's style formed.Researches on white tea's flavors are not systematic, most of which focus on some aspects of white tea's flavor. Some researches are from long-time ago and the materials used in the paper have no definite origin and brands. And the results from different paper are far diverted from each other.There are 14 white tea samples picked from Fujian province which were studied in this paper. This paper mainly researches white tea's flavor characteristic and its antioxidant capacity. We analyzed the constituents and contents of catechins, caffeine, amino acid and volatile compounds for the flavor part. As for antioxidant part, we analyzed tea polyphenol, flavones and ABTS.HPLC was used to determine the contents of six catchins and caffeine at one time, methanol and 2% aqueous acetic acid was the liquid phase. Amino acid was detected by amino acid automatic analyzing instrument, and 18 dissociate amino acid were determined. After analyzing these 14 white tea samples, we got this content sphere of flavor compounds:total catechins from 84.45 mg/g to 170.73mg/g; six catechin monomers are:EGC:1.60-10.01 mg/g; DL-C:1.04-4.79 mg/g; EC:7.34-21.31 mg/g; EGCG:52.54-111.37 mg/g; GCG:0.19-2.85 mg/g; ECG:15.02-35.33 mg/g; caffeine from 28.55mg/g to 52.78mg/g; total amino acid from 1057.13mg/100g to 2014.08mg/100g.To determine volatile compounds, solid phase mirco-extraction was used with GC-MS. A series of alkanes were injected into the GC-MS in order to get retention index (RI) for each peak.SPME was used for extracting aroma from white tea and then GC/MS was used for analyzing. After separating and identifying,47 main volatile compounds were identified in white tea. Although the contents of volatile compounds in different tea samples are varied, the main components are the same. Predominant components are Linalool and its oxide, Geraniol, Phenethyl alcohol and 3-Hexen-l-ol, (Z). It is very different between white tea's style and other tea's which may result from the special long-time withering process. PCA was used to analyze the aroma of 14 samples, and it is found that samples from zhenghe and fuding are diverse in their aroma. Samples from zhenghe have a flower smell and contain sweet, green, fruity characters. And samples from fuding have an odor of freshly cut grass as well as the fresh taste like violet and rose.This paper analyzed the contents of tea polyphenol and flavones as well as the ABTS capacity, giving out some statistic to describe the white tea's antioxidant capacity. As for tea polyphenol, national standard published in 2008 was taken as a reference, using Folin-Ciocalteu as color development reagent and gallica acid as standard working curve. In this paper, flavonols are hydrolyzed and then dedermined with HPLC. ABTS total antioxidant capacity was determined by method of kit which is simple and easy. After experiment, we found that white tea's tea polyphenol content is from 12.98% to 23.30%. the total contents of flavonals are from 17.99 ug/g to 46.74ug/g. The ABTS capacity results are between 24.80umol/l to 157.95umol/l when counted by Trolox equivalent antioxidant capacity. |
PDF Full Text Request