Care must be taken, Mr. Crole says, to arrest fermentation at the proper stage by the first "firing," and this firing expels about half of the remaining moisture of the withered leaves, and probably develops an additional portion of those volatile oils which give fragrance and taste to manufactured tea; and which Mr. Crole designates by the name of "theol." Too high or too long continued firing drives off these oils with the watery juices. They are also wasted by exposure of manufactured tea to the atmosphere. Firing is sometimes divided into two or three stages.
In the above summary we have described all essential treatment of tea leaves necessary to produce manufactured tea.
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.
Both in China and Japan it is the custom to give large portions of the tea crop which are intended for export to foreign countries, only a preliminary drying or curing sufficient to preserve them temporarily. When they arrive at the shipping ports they are subjected to additional firing and thorough drying.
CHAPTER VII.
Chemistry and Physiological Aspects of Tea.
If the reader desires an example of imperfect and arrested knowledge in some of the common affairs of life, let him collate the statements of scientific experts concerning the physiological effects upon mankind, of tea. He will then admit that "in a multitude of counsellors there is confusion."
Without pretending to more than the rudiments of chemical or physiological science, we shall attempt to examine the nature of tea, and its effects upon the human system; taking as a basis for our remarks Professor Jas. F. Johnston's Chemistry of Common Life, from which work more recent writers draw most of their inspiration.
Chemists find in manufacturing tea leaves three principal constituents to which all the physiological effects of tea are attributed. These are, (1) Theine, (2) Essential or Volatile Oils, (3) Tannin.
Theine is present in the green leaf of tea, and is apparently unchanged in the manufactured leaf and in the infusion or beverage. 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. In testing and grading teas for purchase and sale, their appearance, odor and taste, their color and body when "drawn," determine their pecuniary value, without relation to their percentage of theine, or its effects upon the tester.