綠茶於貯藏期間其維生素丙含量變化之研究

Studies on the Changes of Vitamin C Content in Green Tea during Storage

謝伯東(Po-Tung Hsieh) ； 楊建澤(Chien-Tse Yang)

《化學》 58年4期 (1969/12) Pp. 75-79

https://doi.org/10.6623/chem.1969017

摘要

依2,4-dintitrophenylhydrazine之osazone光電比色法定量本省產綠茶於貯藏期間期所含還原型金氧化型維生素丙及2,3-diketo-L-gulonic acid三成分含量之變化，得到如下結果。（1）本法稍加修正，即可適用於綠茶該三成分之分析，（2）該三成分之總含量隨貯藏之進行緩慢減少而氧化型維生丙之含量則於外觀上未見有增減，（3）還原型維生素丙含量與2,3-diketo-L-gulonic acid之含量呈相對消長變化，（4）還原型維生素丙之氧化仍循氧化型維生素丙與2,3-diketo-L-gulonic aci之途徑進行。綠茶係本省主要茶葉產品之一，每年除自給外大部分供為外銷，其數量佔本省茶葉外銷之約五成，居於首位。至於其製造方式，目前仍採傳統方法將生茶葉加工製造，因於貯藏期間未確立完善之品制度，致其製造以及貯藏方式無從再求得改進。綠茶比紅茶或烏龍茶含有多量之維生素丙，不僅屬於嗜好飲料，亦為保健上維生素賽攝取來源之一。但，維生素丙（即還原型維生素丙，L-ascorbic acid，以下簡稱AsA）易受空氣中氧之作用，脱氫需生成氧化型維生素丙（dehydro-L-ascorbic acid, DHA），此DHA會繼續加水分解，產生不具生理效用之2,3-diketo-Lgulonic acid (DKA)，再轉變成低分子物質，由此可知於綠茶之製造或貯藏中研究其維素丙含量之變化頗值得留意。有關此方面之研究，以往發表者並不多，瀧野曾報告綠茶於製造過程中其維生素丙含量之變化，惟並未定量出DKA含量之變化，是故，作者等擬於本研究中挑選維素丙含量特別豐富之新鮮綠茶為實驗材料，進行貯藏試驗，採用光電比較色法定量其AsA, DHA, DKA三成分之含量，期以明瞭綠茶於貯藏期間該三成分含量變化情形，並闡明其變化機構，俾供綠茶之貯藏時品質管理以改進其貯藏方式之參考。

並列摘要

A mudified 2,4-dinitrophenylhydrazine method was used to study the probable changes of L-ascorbic acid(ASA), dehydro-L-ascorbic acid(DHA), and 2,3-diketo-L- gulonic acid(DKA) content in Taiwan green tea during storage. The results obtained were summarized as follows: (1) The method was suitable for the determination of ASA, DHA and DKA content in the extract of green tea. (2) For all samples studied, the total content of the three components was fcund to be gradually decreased with time, while the DHA content shcwed no change in appearance. (3) The analysis for ASA and DKA demonstrated that the loss of ASA was generally accompanied by propor-tionate increase in DKA. (4) The oxidation mechanism of AsA in green tea was in agreement with that of the study which was fcund via the path way of DHA and DKA.