Study On Active Aroma Compounds In Puer Tea

Puer tea was a long history of special tea of Yunnan province in China. It had been a geographical indication product. Because of its excellent health benefits and it was more and more popular in the majority of consumers at home and abroad. Puer tea processing technology was based on the Yunnan big leaves of fresh leaves by fixing, rolling, drying and other processes made green maocha raw materials, then heap fermentation, steaming kneading, molding into various shapes of the finished product Puer tea. The chemical compositions occured the complex changes in the heap fermentation, especially of tea aroma components, enzymolysis, oxidation reduction of catechins and other polyphenols, as well as water, heat and acidic conditions, cound cause or promote the generation of aromatic compounds. This had been the unique quality characteristics and health effects of Puer tea. Many Puer tea researchers had a lot of research on its chemical composition and its variation law in the process, and revealed its relationship with Puer tea quality, but because of the lack of systematic research, it needed scientists and Puer tea lovers’ further research and exploration. Puer tea products lacked of the international market competitiveness, because the aroma was low on one hand. If cound strengthen the research in this regard, and identified that what compounds had a significant contribution to Puer tea aroma. It wound bring greater development of Puer tea products. Effective uses of modern technology wound expand the Puer tea sales, service for the local agricultural economy.Sample preparation adopted static state headspace solid-phase microextraction, and it concentrated volatile organic compounds in typical representative of Puer ripe tea in Yunnan in five different storage times. By means of a preliminary analysis by gas chromatography-mass spectrometry(GC-MS), for volatile components varieties and contents of the five puer ripe teas. Gas chromatography-olfactometry (GC-O) analysed aroma active compositions. What’s more, measuring the thresholds of five methoxy compounds, to further determine the contribution of methoxy compound in Puer tea cooked tea to the overall flavor. Volatile organic compounds were extracted and concentrated by divinylbenzene/carboxen/polydimethylsiloxane fiber in65℃water bath at1h. Then we carried through gas chromatography-mass spectrometry analysis and gas chromatography-olfactometry analysis. Odor compounds were smelled in gas chromatography-olfactometry Sniffer port. The volatile organic compounds were identified by retrieving NIST05mass spectrum, comparing with the retention index (RI) and literature reports, and through the area normalization quantitative. The aroma active compositions in five kinds of Puer teas were defined via the retention index and odor description compared with the corresponding retention index and odor description on literature reports. At the last, via three point text, we measured the thresholds of1,2-dimethoxy benzene,1,3-dimethoxy benzene,3,4-dimethoxytoluene,1,2,4-trimethoxybenzene, and3,4,5-trimethoxytoluene.(1) GC-MS had identified70volatile organic compounds in common in five puer ripe teas. Their identical compounds had29compounds, with methoxy compounds, aldehyde, ketone and alcohols primarily. They were1,2,3-trimethoxybenzene,1,2,4-trimethoxybenzene,1,2-dimethoxy benzene,3,4,5-trimethoxytoluene,4-ethyl-1,2-di-methoxybenzene, dihydro-actinidiolide, β-ionone,6,10,14-trimethyl-2-pentadecanone, geranyl acetone, β-ionon-5,6-epoxide, linalool oxide trans,.alpha.-ionone, naphthalene,(E,E)-2,4-heptadienal,.alpha.-terpineol,2-ethyl-1-hexanol, cedrol, dihydro-β-ionone,1-methyl-naphthalene, benzaldehyde,(E)-2-nonenal, benzeneacetaldehyde, β-cyclocitral, eucarvone, decanal, fluorene,1,4-dimethoxybenzene, isophorone, acetophenone. Of them, higher content compounds were1,2,3-trimethoxybenze-ne,1,2,4-trimethoxybenzene,1,2-dimethoxybenzene,3,4,5-trimeth oxytoluene,4-ethyl-1,2-dimethoxybenzene, dihydro-actinidiolide, β-ionone,6,10,14-trimeth-yl-2-pentadecanone, geranyl acetone, β-ionon-5,6-epoxide, linalool oxide trans,.alpha.-ionone, naphthalene,(E,E)-2,4-heptadienal,.alpha.-terpineol,2-ethyl-1-hexanol,1-methyl-naphthalene, benzaldehyde.(2) GC-0had identified36aroma active compounds in common in five puer ripe teas:hexanal, heptanal, benzaldehyde,1-octen-3-one,1-octen-3-ol, octanal,2-ethyl-1-hexanol, benzeneacetaldehyde,(E)-2-octenal, octanol, guaiacol, nonanal,2-nonanone, linalool, phenylethyl alcohol, isophorone,1,2-dimethoxybenzene, camphor,(E,Z)-2,6-nonadienal,1,3-dimethoxybenzene, naphthalene,.alpha.-terpineol, decanal,3,4-dimethoxytoluene, nerol, geraniol, bornyl acetate,2-undecanone,1,2,3-trimethoxybenzene, cis-jasmone,1,2-dimethoxy-4-n-propyl benzene,3,4,5-trimethoxy-toluene,.alpha.-ionone, dihydro-β-ionone, geranyl acetone, β-ionone. There were an unknown aroma compound (sweet, milk and floral) as well.(3) Three point text measured the odor threshold concentration of1,3-dimethoxybenzene and3,4,5-trimethoxytoluene were both lower in five standard methoxy compounds,86.19ppb,142.26ppb respectively.3,4-dimethoxytoluene,1,2-dimethoxybenzene and1,2,4-trimethoxybenzene were higher than the ones before around10folds, and presented lower aroma. It was the same result as Puer tea fragrance smell.