Agr. Biol. Chem., 39 (6), 1263•`1267, 1975

Flavor Components in Vietnamese Green and Lotus Tea•õ

Thanh-Thi NGUYEN and Tei YAMANISHI

Laboratory of Food Chemistry, Ochanomizu University, Tokyo Received January 23, 1975

The aroma concentrates from Vietnamese and lotus tea were prepared and analyzed. Characterization of the components were carried out using coupled gas chromato graphy and mass spectrometry and infrared spectrometry, besides gas chromatographic retention data. Anethole and 1,4-dimethoxybenzene have been identified for the first time as the flavor constituents in green tea. Linalool, two linalooloxides (cis and trans, five membered), 3,7- dimethyl-1,5,7-octatriene-3-ol, 2,5 (or 2,6)-dimethylpyrazine and 1-ethyl-2-formylpyrrole were the predominant components in Vietnamese green tea. 1,4-Dimethoxybenzene has been identified as the main component in lotus tea. The com pound was also isolated from both dried and fresh lotus pollen.

Tea is an important crop in Vietnam, and immediately mixed with 500ml of hot water (about next to rice and rubber. Tea plant grown in 60•Ž) in the 2 liters flask of ratory evaporator connected Vietnam belongs to the family of Theacease, with a condenser and two traps as shown in the previous paper.1) Distillation was conducted at 50•Ž (water originated from Shan district. Tea scented bath temperature) under reduced pressure at 18 to with lotus pollen, called lotus tea, is purely 20mmHg. When the material in the flask almost Vietnamese special tea and it is the best liked dried, another two portions (500ml of hot water) were and the most expensive in Vietnam. added and distillation was repeated. Thus, about 1.2 liters of distillate was obtained. The distillate in trap A This paper reports on the flavor analysis (cooled by ice-salt mixture) was combined with the con of 1) Bach-mao tea (the highest class of densate in trap B (cooled by dryice-acetone mixture), Vietnamese green tea manufactured by pan saturated with sodium chloride and extracted with firing process) and 2) lotus tea. peroxide-free ether. After drying the mixture with sodium sulfate, the ether extract was concentrated by

EXPERIMENTAL distilling off the ether at 38 to 40•Ž. The pale yellow oil which has an intense typical aroma of tea

Materials was obtained. 1) Bach-mao tea was manufactured by pan-firing The procedure was repeated on another 800g of processing, so called "tra-xao" process, from summer Bachmao tea. Total yield of the aroma concentrate leaves at Nam-Sanh tea company, located on Blao in (I) was 2.6g (0.26%). The distillation for lotus tea was South Vietnam. carried out by the same procedure as above. From 2) Lotus tea was manufactured by private order. 800g of lotus tea 2.58g (0.3%) of the aroma concen

It was scented with natural lotus pollen (600 flowers trate (II) was obtained. This aroma concentrate were used for 1kg of green tea). contained some crystals. 3) Dry lotus pollen, which was separated from

lotus tea. Analysis of the aroma concentrate. Method of identi 4) Fresh lotus pollen. Lotus flower plucked at fication the ponds in suburb of Saigon on August 29, 1973, and Gas Chromatography (GC). Japan Electron Optics

stored at -20•Ž in our laboratory. Pollen were Laboratory Co., Ltd.-Model 810 Gas Chromatograph

separated from flower just before distillation. with a thermal conductivity detector (TCD) was utilized for separation. Experimental parameters are written Preparation of aroma concentrate in each figure of the chromatogram. Each 200g of green tea was mechanically powdered Infrared analysis (IR). IR spectra were recorded •õ Studies on the Flavor of Green Tea. Part XI. on a Japan Spectroscopic Co., Model IR-S, Infrared Presented at the Kanto Branch Meeting of Agricultural Spectrometer and analysed with either a film of the pure Chemical Society of Japan, on June 28th 1974. 1264 T. NGUYEN and T. YAMANISHI sample or with nujol. are listed in Table 1. Gas chromatography was also run on Mass spectral analysis (MS). A Hitachi RMS-4 Mass Spectrometer, combined directly with gas chro packed column and recorded by TCD as well matograph Hitachi K53 with a Bieman-type helium as total ion monitor in GC-MS analysis. separator was used. Experimental parameters are writ The chromatogram recorded by TCD is shown ten in each figure of the chromatogram recorded by in Fig. 2. Identified components and their total ion monitor. compositions are listed in Table II. Compounds were identified by comparing their spec Anethole and 1,4-dimethoxybenzene have tra with those of authentic compounds or with pub lished standard spectra, checking retention time agree never been found as the components of the ments. flavor up to date. The two compounds seemed to be specific to Vietnamese tea RESULTS AND DISCUSSION (variety: Shan). 1) Bach-Mao tea 2) Lotus tea Figure 1 shows the gas chromatogram of Aroma concentrate (II), from lotus tea was aroma concentrate (I) on Golay column separated into four traps by gas chromato (Carbowax 20M) recorded by total ion monitor graphy using column Carbowax 6000 as shown in GC-MS analysis. Identified compounds in Fig. 3-1.

FIG. 1. GC-MS Chromatogram of Bach-Mao Tea Aroma Concentrate.

Column: Golay column, Carbowax 20M, 0.5mm (i.d.)•~45m. Injection temp.: 200•Ž,

Helium flow rate: 3ml/min. Column temp.: 40•Ž_??_60•Ž _??_170•Ž (hold 11 min)

_??_190•Ž. Detector: Total ion monitor. Helium separator temp.: 200•Ž, Ionization source temp.: 200•Ž, Electron energy: 70eV.

TABLE I. IDENTIFIEDCOMPONENTS IN BACH-MAOTEA VOLATILES (Reference to Fig. 1)

a) Electron energy: 70eV . Scanning speed: 6 sec. Flavor Components in Vietnamese Green Tea and Lotus Tea 1265

FIG. 2. Gas Chromatogram of Bach-Mao Tea Aroma Concentrate.

Column: 3mm (i.d.)•~300cm stainless steel. Column packing: 23% Carbowax 6000 on Shima lite W 60/80. Injection temp.: 180•Ž, Helium flow rate: 30ml/min. Column temp.: 40•Ž

_??_ 180•Ž. Detector: T.C.D.

TABLE II. IDENTIFIEDCOMPONENTS AND THEIR COMPOSITIONS IN BACH-MAOTEA VOLATILES (Reference to Fig. 2) Mass spectra of peaks 23, 24 and 25 were not clean and could not be characterized.

FIG. 3-2. GC-MS Chromatogram of Trap 2. FIG. 3-1. Preparative Gas Chromatogram of Aroma Column: Golay Column, Carbowax 20M, 0.5mm (i.d.)•~ Concentrate from Lotus Tea. 45m. Injection temp.: 200•Ž, Helium flow rate: Column: 3mm (i.d.)•~300cm stainless steel. Column 3ml/min. Column temp.: 40•Ž_??_60•Ž_??_ packing: 23% Carbowax 6000 on Shimalite W 60/80. 170•Ž.

Column temp.: 75•Ž_??_180•Ž. Detector: Total ion monitor. Detector: T.C.D. 1266 T. NGUYEN and T. YAMANISHI

FIG. 4. IR and Mass Spectra of Trap 2 from Lotus Tea Aroma Concentrate.

Fig. 4. Natural occurence of 1,4-dimethoxy benzene has been only reported as a miner component of essential oil from flower of lilac (Syringa vulgaris L.).2) The components in the other three traps were the same as those in the aroma concentrate from Bach- Mao tea.

3) Isolation of 1,4-dimethoxybenzenefrom both dry and fresh lotus pollen Since 1,4-dimethoxybenzene was identified FIG. 5. GC-MS Chromatogram of Aroma Concen trate from Lotus Pollen. as the main aroma constituent in lotus tea, aroma concentrates were prepared from both (A), dried pollen, (B), fresh pollen. Column: 3mm (i.d.)•~300cm stainless steel, Column dry and fresh lotus pollen and analyzed by packing: 23% Carbowax 20M on Shimalite W 60/80. the same procedure as mentioned above. As Injection temp.: 200•Ž, Helium flow rate: 30min/ml. the result, 1,4-dimethoxybenzene was found Column temp.: 75•Ž_??_180•Ž. Detector: total in amount to 93% of aroma concentrate ion monitor. prepared from dry pollen, and 30.4%, of that from fresh pollen. The chromatograms Trap No. 2 was obtained as crystalline are shown in Fig. 5. form. Rechromatogram of trap No. 2 after dissolving with ether, on column Carbowax Acknowledgement. We wish to thank to Mr. Nguyen 20M, showed only one peak (peak A) besides Quoc Dong, Saigon Water Works Department for solvent peak. GC retention data, IR and MS the supply of lotus flowers and also to Mr. Tang Kim Tay, Minh-sanh Tea Co. and Mr. Ut, Nam-sanh Tea of peak A were entirely identical with those of Co. for their generous supplies of Vietnamese green authentic 1,4-dimethoxybenzene as shown in . Flavor Components in Vietnamese Green Tea and Lotus Tea 1267

REFERENCES Biol. Chem., 34, 599 (1970). 2) S. Wakayama, S. Namba and M. Ohno, Nippon 1) T. Yamanishi, M. Nose and Y. Nakatani, Agr. Kagaku Zasshi, 92, 256 (1971).