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Updated: May 31, 2025
Chemists find in manufacturing tea leaves three principal constituents to which all the physiological effects of tea are attributed. These are, Theine, Essential or Volatile Oils, Tannin. Theine is present in the green leaf of tea, and is apparently unchanged in the manufactured leaf and in the infusion or beverage.
The coffee-berry a mean of 1.00 per cent. "Besides the theine and the essential oils, which latter give the aroma of the plants, there is contained in both coffee and tea a certain amount of difficultly soluble vegetable albumen, and in the latter, especially, a large quantity of tannin. Roasting renders volatile the essential oil of the coffee-berry.
We regard it as the one essential and the most valuable element of all teas, physiologically considered. Strangely enough theine is the one important constituent which is entirely neglected by the tea-tester and the trader.
While theine is credited as the source of the most powerful and useful properties of tea, and without which no plant would be recognized as tea, yet some of the stimulating or exhilarating influences of this plant are attributed to the volatile oils which contribute so largely to the flavors and odors which characterize tea.
W. M. Green reported that in prolonging the steeping of tea from 10 to 20 minutes, he observed the formation of a tannate of theine, which diminished the proportion of 1.30 per cent. of theine at 10 minutes to 1.16 per cent. after 20 minutes steeping, a loss of about 10 percent., unless the latter salt so formed is proved to yield up its theine constituent in the human stomach.
With the exception of Mate, not one of the above named substitutes for Chinese tea contains the peculiar nerve stimulating and nerve refreshing constituent upon which depends the physiological value of Black or Green tea, the Theine: nor do they possess the characteristic flavoring principle or essential oil which distinguishes commercial teas from all other known plant products.
In manufactured tea leaves, theine constitutes from one to five percent. of their weight. According to Professor Johnston, three or four grains per day of this substance may be taken without injury by most persons; or such quantity as would be contained in half and ounce of Chinese black tea. Theine is soluble in about 100 parts of hat water.
Average of 6 samples Ceylon tea: Theine 3.15 Tannin 5.87 Average 12 samples of Indian tea: Theine 3.63 Tannin 6.77 Theine, per cent infusion 2.79 Increase about 10 per cent Tannin 3.78 Increase about 25 per cent Average of 6 samples Ceylon tea: Theine 3.29 Increase about 5 per cent Tannin 7.30 Increase about 25 per cent
To procure the extreme type of Black teas, a Souchong or Congou, the fermentation or oxidation, and the "cooking" process, is simply carried further, and with higher roasting, some of the volatile oils and delicate flavors are expelled, or are changed into other flavors. Judging by diminished effects upon tea drinkers, some of the volatile theine is also lost.
Caffeine, now found identical with theine, but varying in amount in different varieties of coffee, being in some three or four per cent, in others less. The most valuable property of coffee is its power of relieving the sensation of hunger and fatigue.
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