12份福建乌龙茶的同步热分析
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摘要
采用同步热分析仪研究12份福建乌龙茶茶样的热分解过程.试验条件为:茶样由室温以10℃·min-1匀速升温至600℃,气氛为空气,铝坩埚加盖(盖上钻1 mm的孔).结果表明:茶叶的热分解过程分为5个失重阶段:1室温至100℃左右主要为脱水阶段;2100-226℃为茶叶挥发物逸出阶段;3226-345℃为变味热分解阶段;4345-482℃为碳化阶段;5482-600℃为燃烧阶段.茶叶具有相似的失重过程,差示扫描量热法(DSC)曲线体现茶叶的特征,阶段2主要体现茶叶内含物的品质特征,阶段345主要体现茶叶的纤维素、半纤维素和木质素及粗蛋白、粗脂肪和无机盐等其他物质的含量特征,可反映不同品种、季节和加工工艺茶叶组成的差异.因此同步热分析可作为一种初步的鉴别方法.
10 kinds of Fujian oolong tea were studied by STA449 F3- Jupiter simultaneous thermal analyzer( NETZSCH STA449F3-Jupiter). The test conditions: from room temperature to 600 ℃,heating rate of 10 ℃ ·min- 1,atmosphere of air,aluminum crucible plus with 1 mm diameter hole cover. The results showed that,the pyrolysis process could be divided into five stages,including drying stage of the temperature from room to 100 ℃; escape of volatiles stage of 226 ℃; flavor changing stage of the temperature from 226 ℃ to 345 ℃; carbonization pyrolysis stage of the temperature from 345 ℃ to 482 ℃; thermogravimetry( TG) and microthermogravimetry( DTG) curves of tea are similar,but differential scanning calorimetry( DSC) curves are different,they can reflect the characteristics of tea. The second stage reflects the inclusion quality,last 3 stages reflect the content of hemicellulose,cellulose,lignin and other substances. They also reflect the difference of inclusions of different varieties,season and processing. Simultaneous thermal analysis of tea can also be used as a preliminary identification method.
10 kinds of Fujian oolong tea were studied by STA449 F3- Jupiter simultaneous thermal analyzer( NETZSCH STA449F3-Jupiter). The test conditions: from room temperature to 600 ℃,heating rate of 10 ℃ ·min- 1,atmosphere of air,aluminum crucible plus with 1 mm diameter hole cover. The results showed that,the pyrolysis process could be divided into five stages,including drying stage of the temperature from room to 100 ℃; escape of volatiles stage of 226 ℃; flavor changing stage of the temperature from 226 ℃ to 345 ℃; carbonization pyrolysis stage of the temperature from 345 ℃ to 482 ℃; thermogravimetry( TG) and microthermogravimetry( DTG) curves of tea are similar,but differential scanning calorimetry( DSC) curves are different,they can reflect the characteristics of tea. The second stage reflects the inclusion quality,last 3 stages reflect the content of hemicellulose,cellulose,lignin and other substances. They also reflect the difference of inclusions of different varieties,season and processing. Simultaneous thermal analysis of tea can also be used as a preliminary identification method.
引文
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[2]李晓翔,舒新前,李刚,等.3种农林生物质的热解及动力学研究[J].可再生能源,2010,28(6):63-70.
[3]聂光华.不同产地茶叶的热分析鉴别[J].湖北农业科学,2004(5):77-78.
[4]聂光华,何丽.芭蕉茶叶和伍家台茶叶的热分析研究[J].湖北民族学院学报,2004,22(3):61-63.
[5]郑月梅,郑德勇,叶乃兴.茶叶高温化学的研究进展[J].福建茶叶,2011(4):9-12.
[6]王寅,王海晖,朱凤,等.树叶组成的热解反应及热稳定性的理论解析[J].林业科学,2012,48(11):99-106.
[7]钟秋生,陈常颂,游小妹,等.金萱加工工艺与品质分析[J].茶叶科学技术,2011(1):27-29.
[8]林光华,陈玉成,佘成法,等.东方美人茶加工工艺及适制品种试验初报[J].试验研究,2008(12):16-17.