The Analysis On Characteristic Flavor Components Of Pu-erh Tea

Pu-erh tea is a dark tea which is one of Chinese six tea brands. It has a very long history and profound cultural connotations. It originated in Xishuangbanna, Simao, Chuxiong, Red River, Dali area of Yunnan Province of China. Pu-erh tea is created from sunlight-dried maocha which processed from the fresh leaves of " large leaf" vartieties of camellia sinensis var. assamica through some procedures such as sunlight dry, twisting and solarization, then were made to different forms of commercial Pu-erh tea after post-fermentation. The pile-fermentation processing technology making Pu-erh tea has many unique quality characteristics, include the brown-red appearance, brightly and densely red liquor, the specific mellow aftertaste flavor and bouquet.Some researchers have made part of study on the flavor components of Pu-erh tea. These studies mainly are the impact of different processing techniques and the comparative study of volatile substances between the Pu-erh tea and other tea brands. But their study contained in a involving small samples, not form a system.This article is selected 15 Pu-erh raw tea samples and 15 Pu-erh riped tea samples from Xishuangbanna, Lincang, Dali, Baoshan and Simao five areas of yunnan Province, to study the characteristics flavor compounds of Pu-erh tea. It Mainly studies the composition and content of the characteristic components of water, catechins, caffeine, TF, TR, TB and aroma, then makes a more comprehensive and systematic analysis. Attempts to explain the characteristics flavor components of Pu-erh tea.Simultaneous detection of five kinds of catechins and caffeine is used HPLC method Content of methanol and 2% acetic acid has used be the mobile phase in gradient elution in 32min. The analysis of 30 tea samples are showed the content of catechins in Pu-erh riped tea samples are:EGC: 0.79mg/g-3.72mg/g; DL-C:0.28mg/g-2.30mg/g; EGCG:0.18 mg/g-2.7mg/g; GCG:0.04mg/g-0.31mg/g; ECG:0.24 mg/g-1.75mg/g, total:1.56 mg/g-7.30mg/g. The content of catechins in Pu-erh raw tea are:EGC:6.58 mg/g-14.32mg/g; DL-C:5.84mg/g-13.60mg/g; EGCG:38.69 mg/g-68.05mg/g; GCG:0.28mg/g-0.49mg/g; ECG:34.00mg/g-50.75mg/g; total:99.10 mg/g-132.32 mg/g. The content of catechins in Pu-erh raw tea is observably higher than Pu-erh riped tea. of caffeine in Pu-erh riped tea and Pu-erh raw tea both are about 4%. The content of TF, TR and TB in Pu-erh riped tea is determined by Spectrophotometer. The results showed that the content of TF 0.12%-0.31%, the content of TR 0.98%-2.47%, the content of TB 9.49%-13.72%. The content of TB is much higher than TF and TR. The TB is one of the key factors on Pu-erh riped tea quality.To determine volatile compounds, solid phase mirco-extraction (SPME) 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. Use PCA (principal component analysis) method to analyze the data. The results show that the characteristics aroma components of Pu-erh tea include Hydrocarbons, Alcohols, Esters, Aldehydes, Ketones, etc.. Linalool and its oxides are the main aroma components in Pu-erh tea.Other characteristics aroma components of Pu-erh riped tea are Damascenone; a-Ionone; 2-methoxy-4,4-dimethy1-2-cyclohexenyl-1-one;β-Ionone; 1,2-methoxybenzene; 2,3,6-trimethyl-7-Octen-3-ol; 1-methoxy-4-(1-propenyl) benzene; Longifolene; Geranyl acetone; a-Cedrene; Phytone; Dihydro-actinidiolide; 1,2,3-trimethoxybenzene and other compounds. Other characteristics aroma components of Pu-erh raw tea are a-Ionone; 2-butyl hydroxy toluene;β-Ionone; a-cedrene; Eugenol; trans-2-Pinanol; Dicyclohexyl-methanone; Benzoic acid,2-hydroxy-, methyl ester; Dibutyl phthalate; 1,2-Benzenedicarboxylic acid, bis(2-methylpropyl); Octadecanoic acid, methyl ester; Hexadecanoic acid, ethyl ester; cis-Jasmone; Phytol and other compounds. The analyses indicate that Pu-erh raw tea contains more Esters than Pu-erh riped tea. Pu-erh riped tea contains more Methoxybenzene substances than Pu-erh raw tea.The PCA analysis of aroma on all samples indicate, the composition and content of aroma substances include Benzene,1,2-dimethoxy-; Damascenone, Linalooloxide(furanoid); Linalooloxide (furanoid), Linalooloxide (pyranoid); Benzene 4-ethyl-1,2-dimethoxy-; 2-Methoxy-4,4-dimethyl-2-cyclohexen-1-one; Cyclohexanecarboxylic acid,4-butyl-, 4-propoxy phenyl ester; Hexanoic acid,3-tridecyl ester; Dihydroactinidiolide; 1H-Pyrrole-2-carboxaldehyde,1-ethyl-; a-Terpineol; Benzene,1,2-dimethoxy-3-methyl-; 1,2,3-Trimethoxy benzene, trans-2-Pinanol; Benzene,1-methoxy-4-(1-propenyl)-can be the basis to distinguish the Pu-erh riped tea and Pu-erh raw tea.