Theine—3.63 Tannin—6.77
STEEPED 10 MINUTES.
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
Average 12 samples of Indian tea:
Theine—3.73—Increase about 3 per cent Tannin—8.09—
Increase about 20 per cent
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.
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.
These Essential or Volatile Oils of manufactured tea are said to reside in the minute cells of the green leaf, but they are greatly changed by manipulation, for they are not manifest to the sense of taste or smell when expressed from the green leaf by bruising, nor does the green leaf yield their aromatic flavors to an infusion. Professor Johnston says that these precious oils are artificially developed by manufacture. David Crole declares that they are developed "to a certain extent during withering, and also during the first stage of firing," which last process, if carelessly conducted, "oxidises it (the oil) into resin."