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題名 | 水質、pH及金屬離子對烏龍茶茶湯色澤及多元酚含量之影響=Effects of Water Quality, pH and Metal Ions on the Color and Polyphenol Content of Oolong Tea Infusion |
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作者 | 陳清泉; 尤新輝; 程竹青; | 書刊名 | 食品科學 |
卷期 | 24:3 1997.06[民86.06] |
頁次 | 頁331-347 |
分類號 | 473.4 |
關鍵詞 | 烏龍茶; 水質; 多元酚; 金屬離子; Oolong; Water quality; Polyphenol; Metal ions; |
語文 | 中文(Chinese) |
中文摘要 | 萃取水水質對烏龍茶茶湯之品質,包括外觀色澤、香味及滋味(多元酚化合物含量) 等的影響主要可以分成兩種效應,即 pH 效應及離子效應。萃取水的 pH 越高,則萃取所得 茶湯之 pH 也越高,而在高 pH 環境下,多元酚化合物容易進行氧化,導致烏龍茶茶湯中多 元酚含量降低。金屬離子則可以與多元酚形成複合物,然後進一步催化多元酚的氧化反應。 實驗結果顯示,萃取水之 pH 越高,則萃取所得烏龍茶茶湯之外觀色澤越暗紅,香味也類似 紅茶,多元酚類成分含量則越低。以檸檬酸╱碳酸氫鈉調整萃取水之 pH 所造成的效應較以 鹽酸╱氫氧化鈉調整 pH 所造成者明顯。 自來水雖然水質不佳, 但若以鹽酸調整 pH 到 5.5-6.5 左右,則可獲得外觀色澤較佳的茶湯,對多元酚化合物的氧化現象也可大幅降低。 Fe(II)、 Fe(III) 及 Cu(II) 等金屬離子催化多元酚化合物氧化之最低濃度分別為 20、20 及 5 ppm。添加碳酸鈣於萃取水中,則碳酸鈣解離後鈣離子具有離子效應,而碳酸根離子則 具有 pH 效應,比較添加碳酸鈣與氯化鈣之影響,可以獲知,pH 效應遠較離子效應為大。 |
英文摘要 | The effects of the pH and hardness of extracting water on the quality of oolong tea infusions, including effects on the color, flavor and taste, could be categorized into two major effects, a pH effect and an ionic effect. Experimental results showed that higher pH of the extracting water led to rapid oxidation of polyphenols and resulted in a significant decrease in the polyphenol contents of the oolong tea infusions. The color and flavor of the oolong tea infusions, when extracted with a water solution of higher pH value, were also found to be much more similar to those of black tea infusion. Metal ions, especially the divalent metal ions, formed complexes with polyphenols readily and then catalyzed the oxidation reaction of polyphenols. The effect of citric acid/sodium bicarbonate on the quality of oolong tea infusions, when used to adjust the pH of the extracting water, was found to be more significant than that of hydrochloric acid/sodium hydroxide. Tap water, although not quite suitable as an extracting solution due to its high pH and hardness, could be improved by acidifying the pH to 5.5-6.5 via addition of hydrochloric acid. The minimal concentrations required to cause a significant decrease in the polyphenol contents of the oolong tea infusions of Fe(II), Fe(III) and Cu(II) ions were found to be 20, 20 and 5 ppm, respectively. Both the pH and ionic effect could be observed when calcium carbonate was dissolved into the extracting water. The pH effect on the quality of oolong tea infusions was found to be more significant than the ionic effect. |
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