VARIOUS METHODS OF PREPARING FOR USE.
In China, where tea has been in use from time immemorial, and where it not only forms the regular beverage of the people but also administers to the luxury of the epicure, it is generally prepared in the cup. The tea service consists of large porcelain cups which fit into a silver base, a smaller cup and cover, the leaves being placed in the large cup which is filled with boiling water and also covered. In about two minutes when the tea is drawn it is decanted from the large to the smaller cups, the cover being used to strain off the tea, after which it is drank without the addition of either sugar or milk. Another shorter method is to first put a small quantity of leaves in a cup and place a perforated silver-lid on top to keep them down, briskly boiling water is then poured on and the cups covered with a saucer to prevent the aroma from escaping. The tea is then allowed to brew or “draw” in this manner from eight to ten minutes, after which the infusion is drank from the original cup. By these simple processes only the more volatile and stimulating properties of the leaves are extracted the tannin or astringent principle being retained in the leaves and an immeasurably much finer beverage produced than by any other known method.
The Mandarins and wealthier Chinese prepare it in a small hollow ball made of either gold or silver, about the size of a walnut, suspended from a finger-ring by a slender chain of the same material four to five inches long. This “tea-ball” is divided in the middle, the halves being hinged and perforated with innumerable holes, but is often made like a globular sieve of gold or silver wire connected in the same manner. The halves are filled with tea-leaves and then clasped tight and suspended by the ring and chain from one of the fingers of the right hand into a porcelain cup of freshly boiling water and gently moved to and fro or up and down until the water is colored to the desired height, the strength of the infusion thus prepared depending much on the length of time the tea-ball is agitated in the cup, making it strong or weak as may be required. The Chinese invariably make the infusion with rain or spring water heated to a high degree, the ebullition lasting only a few minutes and poured on the leaves just as soon as the bubbles appear on top of the water.
The Japanese, to whom tea is as valuable as it is to the Chinese, first reduce the leaves to a fine powder by grinding them in a small hand-mill made for the purpose, and then mix it with hot water to the consistency of a thin pulp, in which form it is sipped, not drank, particularly by the aristocracy and richer people, being made and served to visitors in the following manner: The tea-table, with the powdered tea enclosed in a box, is set before the company and the cups filled with boiling water as much of the powder as would cover the point of a knife put into each cup, which is then stirred and mixed with a curious denticulated instrument until the liquor foams, in which state it is served to the company, and sipped while warm. Customarily they strain the liquid before drinking, but frequently the tea and pulverized leaves are drank together in the same manner that the Turks and other Orientals use coffee.
In Cashmere a beverage called “Cha Tulch” is prepared from tea by boiling the leaves in a tin-lined copper pot to a strong, dark decoction, and while boiling briskly phule (red potash), anise-seed and a little salt is added, after which it is poured into a kettle and finally served in porcelain tea-cups. It is also prepared there in a vessel termed a Chajos—kettle and tea-pot combined—and poured direct into the cups, but is used only after meals, more particularly after the morning repast. The morning meal, consisting of this decoction and some plain biscuit served hot. Another preparation, known as “churned tea,” made in a similar manner, but afterwards regularly churned like milk, is highly prized among them, being used exclusively for entertaining visitors. And there is no doubt that the Cashmere ladies talk scandal, vent their grievances and discuss their bonnets and their babies over this peculiar beverage in the same manner as do their more civilized sisters in America at their “five o’clock teas.”
Vumah cha or “Cream tea” is the favorite form in Turkestan in the preparation of which only Black tea is used, but is a much stronger decoction than that ordinarily made. The leaves are boiled in a copper pot and the color heightened by lifting spoonfuls up and letting them fall back again into the vessel while boiling, cream being added to it meantime and bread soaked in it, after which it is eaten. Another preparation termed Seen cha or “bitter tea” is made from Green tea infused in the regular way, but drawn for a shorter time, as the lighter the color the higher it is valued.
The Persians boil the leaves in a pot or kettle until the water assumes a blackish color and bitter taste, after which they add fennel, anise-seed, cloves and sugar to it, while the Hindoos and Cingalese simply put the leaves in seething water and use the liquor only without the addition of any other ingredient. In Chinese-Tartary tea is prepared in the customary manner as with us, but the liquor and leaves are swallowed together. The Mongols generally add milk, but make a much stronger decoction and use only the infusion, while the Bokharis use only Black tea mixed with camel’s milk or suet, breaking up their bread in it, always carrying a bag of it with them when traveling, giving it to their innkeepers to brew as they need it.
In Siam when the water is well boiled they pour it on the leaves which have been put in an earthen pot proportional to the quantity they intend to make, the ordinary amount being as much as they can take up with the finger and thumb to a pint of water. They cover the pot until the leaves have sunk to the bottom and then serve it up in china dishes to be drank as hot as can be endured without sugar or milk.
A preparation called Shamma or “residue” is made from the spent or exhausted leaves—that is, leaves once used—in Beloochistan, and chewed like the pan or betel-leaf is in India and the coca in South America, and is claimed to have the same exhilarating effect in enabling them to stand fatigue and long journeys.
Tea is prepared for use in Thibet by first grinding the leaves and mixing them with bullock’s blood. This compound is then pressed into the form of bricks, dried by a fire-heat and wrapped in sheepskin until required for use, in which form it also serves as a currency throughout Central Asia. A kind of “bouillon” or soup is made from them by boiling in water and adding salt flour, oil, tallow or camel’s milk.
Among the Arabs tea is prepared by first placing a large kettle over a wood fire to heat and then filling it with water, the leaves being meantime mixed with salt and thrown into the water as it heats. When it approaches the boiling point they are rapidly stewed and lifted with a large ladle until the liquid becomes dark brown, when it is poured into another vessel, the kettle being cleaned meanwhile and a paste composed of meal and butter put in to fry in it. The tea infusion with cream added is then poured on the whole, ladled as before, after which the mass is removed and set aside to cool. In this condition it is ladled into wooden mugs and served up, the decoction thus prepared forming both meat and drink, satisfying hunger and thirst at the same time.
Tea in Morocco is regarded as a “course meal” the tea-pot or kettle is first filled with Green tea, sugar and water in such proportion as to make a thick syrup, which is used without the addition of milk or cream, but frequently add spearmint, wormwood, verbena, citron, and on great occasions ambergris. It is usually drank while seated cross-legged on soft carpets, spread on the floor around a costly tray with small feet raising it a few inches from the floor, furnished with glasses in place of cups, nothing else being taken at the meal. An infusion made of tea and tansy is also a favorite beverage with the people of Morocco which is highly aromatic and tonic in its effect, and claimed by them to be a remedy for debility.
In Switzerland it is customary to mix cinnamon with the leaves before making the infusion, and brew both together at the same time in the usual manner. While in France and other continental countries brandy, wine, or other liquor is generally added to the beverage before drinking.
The Russians, who are a nation of tea-drinkers, and who are close enough to the Chinese to have received some knowledge of their methods of preparing tea for use, are very particular in using fresh-boiled water. They prepare it in the same manner as with us, sliced lemon being invariably added to the infusion before using, which wonderfully improves the flavor, making a delicious beverage. Sugar or milk are seldom added, but in cold weather a kind of liquor called “Vodki” is substituted for the lemon, the latter making it a potent drink, sending a glow all over the body. The vessels used by Russians in making tea consists of a small china tea-pot and a “Samovar” invariably, but the tea is not brewed or “drawn” in this vessel as is generally supposed, it being simply the utensil in which the water is boiled, taking the place and serving the same purpose as our tea-kettle. It is usually of brass, though often of other metal, urn-like in shape, but, unlike an ordinary urn, having an inner compartment or cylinder running through the middle, in which is placed burning charcoal for heating the water to an extreme temperature on the principle of a tubular boiler. The charcoal is not lighted until the Samovar is placed on the table, the water being drawn on to the tea as required, the tea being first put in a porcelain or earthenware tea-pot and filled from the Samovar; the first water is poured off the tea as soon as it is put on, being used merely to carry off the dust. A second water is then used for drawing the tea, sufficient to make a strong infusion, being poured on at once, after which the tea-pot is covered, an ample “cosy” being fitted over it to keep the tea warm and prevent the aroma from escaping, and is then allowed to draw from four to five minutes. Sufficient of this beverage is poured into each cup or glass and a slice of lemon added, as tea is drank chiefly from glasses set in metal frames in Russia, and the glass refilled with boiling water from the Samovar.
It is strange that nothing is ever done in this country by dealers to attempt to educate or enlighten their customers how to properly prepare their tea, study the water or preserve its aromatic properties after purchasing, seeing, as they must, how little the art is understood in this country particularly. Good tea can be kept intact, like good wine, for years with considerable advantage to both dealer and consumer alike, and there is no valid reason why consumers of tea should not be as particular and fastidious as buyers of wine. But to obtain good tea in the first place the consumer should purchase only the best, it requiring much less of the finer grades to make a good infusion—purchasing only from the most reputable dealers, those who know or study to understand their business. As a nation, the American people want the best of everything, or, as they characteristically express it, “the best is good enough for them,” and they intend to have it if money can purchase it. But of what avail is the best—tea for instance—if it be not prepared properly or in such a manner as to develop and secure its more delicate, subtle, volatile, refreshing and exhilarating properties. A country that expends annually upwards of sixteen millions of dollars on this commodity alone ought to devote a little more time and trouble in studying the best methods of preparing it and in extracting its most desirable and fragrant qualities.
Tea may be made depressing and injurious, or exhilarating and wholesome, according to the manner in which it is treated and prepared for use. Many who imagine that a high, dark-colored liquor indicates strength, boil the leaves, while others, again, spoil the tea by putting the leaves into the boiling water, some people putting the leaves in cold water and then placing the vessel over the fire to boil, prolonged infusion being still another serious mistake. All of these methods produce the same evil results—that of extracting an increased amount of the tannic acid—thereby destroying the flavor of the tea by giving it a bitter and astringent taste as well as imparting an almost ink-black color to the infusion.
The falsely economical custom of filling the tea-pot a second time without removing the exhausted leaves is another error in the making of tea, as the theine which is only soluble in fresh-boiled water, is wholly extracted in the first drawing and cannot for this reason be present in the second, the latter being merely a decoction composed chiefly of tannin. To avoid this error a sufficient quantity of tea should be made in the first drawing or fresh leaves supplied as needed. And still another reprehensible practice is that of adding fresh leaves to those that have already been used once, it being utterly impossible to add either to the strength or flavor of tea by putting more leaves in the tea-pot after the first drawing, for the reason that tea-water will not extract the active principle—theine—from the dry leaves of fresh tea; only fresh boiling water will do this. The use of tea-water simply increases the amount of tannin, darkens the color, destroys the flavor and only adds to the quantity of leaves already in the pot without in the least affecting the active principle, so that if it be necessary to increase the strength of the tea prepared, draw some fresh leaves in a separate vessel and add the liquor to that already made.
Tea being an infusion, not a decoction, it should be brewed, not stewed, the object being to extract as much of the theine or refreshing principle and as little of the tannin or astringent property as possible, without, at the same time, either boiling or overdrawing. So that in the proper preparation of tea for use, the aim and object should be to extract as little of the tannin as possible and as much of the theine and volatile oil as can be conveniently extracted without permitting the infusion to boil, to obtain which most desirable result the following general rules are recommended: Put the requisite quantity of leaves in a covered china or earthenware vessel—avoid tin or metal of any kind, even silver—then pour on fresh, briskly-boiling water and let stand where it will keep hot without boiling from seven to ten minutes according to the variety of tea used. In this time, while the tea is drawing, only the refreshing and stimulating principles (theine and volatile) are extracted from the leaves. Boiling or prolonged infusion dissolves and brings out the astringent principle (tannin) which injures the nerves and impairs digestion, for which reason no tea that has been either boiled or overdrawn is fit to drink. When tea has been boiled or overdrawn it can be readily detected by the exceedingly dark color of the liquor, as well as by its bitter and astringent flavor.
To insure a really good “cup of tea” the kettle must be filled with fresh water—if distilled the better—and boiled for about three minutes; there will be a sparkle about tea made with fresh-boiled water that it cannot receive from flat, hot water, which has been boiled long or repeatedly. For moderate strength it requires one heaping teaspoonful of good tea to each half-pint of boiling water or an ordinary tea-cup half-full to a quart of water will make a sufficiently strong infusion for five persons. No metal vessel, not even one of silver, is fit to make tea in, nothing being better adapted for the purpose than the old-fashioned tea-pot of heavy, glazed, brown earthenware, covered with a tea-cosy—a tufted cushion, cap-shaped, which envelopes the tea-pot, keeping the tea warm and the aroma from escaping. This vessel must be first “scalded” and set on the range to dry and keep hot, after which the tea is put in and allowed to heat for a few minutes before the boiling water is poured on the leaves, and the infusion allowed to draw or “brew” from five to ten minutes according to the variety of tea under treatment.
India and Ceylon teas are usually “drawn” in five minutes, longer infusion, owing to their great excess of tannin, making them still more bitter and astringent than they naturally are under ordinary conditions. The addition of extra quantities of milk and sugar, however, greatly modifies their great strength, sharp pungency and pronounced flavor. China Green and Japan teas require from six to eight minutes to “draw” thoroughly, while China Oolongs are best at from eight to ten. China Congous yielding lower percentages of tannin than most other varieties, the time allowed should be longer than ten minutes if a full yield of their best properties should be desired. They will also be found more suitable to temperaments to which teas containing larger quantities of tannin are found injurious or objectionable. China teas in general do not require much milk or sugar, while Japans are more pleasing and palatable without the addition of either.
Everything should be clean, the water fresh and the tea drawn at a specific heat, to insure which requires a brisk fire or gas heat, and different treatment according to the season of the year. Care should be taken that the water boils, it being much better to let it boil for a few minutes than use it under the boiling point. In winter the vessel should be made hot and the leaves heated in it before the water is poured on, for about a minute, while in summer the tea-pot need not be heated or the water poured on while boiling, but should be allowed to cease for a few seconds, more or less, according to the heat of the day. It is also a needless operation to pour a small quantity of water on the tea for a preliminary drawing, as is frequently done. Always fill the tea-pot, or pour in at once the quantity required, but for the more temperate seasons a modification of these methods may be adopted. The longest time that any tea should be allowed to steep is from five to ten minutes. As soon as it has been steeped this length of time, at the outside, it should be served. Even if it is allowed to remain on the stove a few minutes after this time it will be ruined.
The character of the water used greatly influences the liquor and flavor of the tea. Soft water should always be used when available, it being next to impossible to make good tea with hard water. Excess of lime in the water also deteriorates the infusion, the last difficulty may, however, be remedied by the judicious use of carbonate of soda, as much as would cover the face of a dime being sufficient for an ordinary drawing of tea.
Tea being an extremely delicate and sensitive article, it should be protected from all foul and foreign flavors, its susceptibility to the odors of other articles being a source of danger and deterioration, as it readily absorbs the smell of coffee, cocoa, spices, meats, fish and other commodities of pronounced flavor. Even when securely packed in the lead-lined chests in which it is received from the producing countries, the change from the glowing heat of Eastern skies to our atmosphere deprives it of much of its pleasing fragrance. For this reason the complaints so frequently made would not arise if always kept in places free from contagion or stored in a dry, warm temperature and not exposed to atmospheric influences.
BEVERAGES PREPARED FROM TEA.
Iced Tea—Put the requisite quantity of leaves in an earthen vessel and pour on briskly boiling water until the vessel is nearly full, and let it infuse or draw from two to three minutes; in no case permit it to boil, as boiling or long infusion extracts the tannin and imparts to it, even the best tea, a disagreeable, herby or astringent taste. When infusion is complete, strain the liquor out of the tea-pot into a jar, demijohn or other covered receptacle, and place it in a cool place for a few hours, or until wanted, then serve in a cup or goblet, adding some cracked ice and a slice or two of lemon. A fine grade of Chinese Congou or Souchong is best adapted for this purpose. Choice Oolong is also good, but Japan tea should never be used, as it is not pleasing when iced to a well-regulated palate. Fine Imperials and Young Hysons are also excellent for those whose nerves can stand Green tea, the first two, however, are best of all, having an especially agreeable flavor when iced. Plenty of ice is needed, which should be cracked, not crushed, and the lemon cut in quarters, the juice being squeezed out and the pulp scraped into the tea. The rind should never be used, as the oil contained in it imparts to the beverage a bitterish taste; use neither milk or sugar unless you are compelled to from habit. It is the bitter flavors of the tea and lemon together that is required to allay the parched feeling of the palate and throat.
Extract of Tea—In hot weather an infusion of tea-leaves made in cold water is much superior to that made in hot or boiling, for the reason that the aroma will not be dissipated. An extract made in this manner may be bottled, and if placed in a moderate temperature will keep for any reasonable time until required for use. When serving, fill the glass with cracked ice, put some sugar on top of it, add a slice or two of lemon and then pour on the extract thus made; the result will be a nectar fit for the gods.
Essence of Tea—Is produced from the leaves by distillation in the form of a dark-colored fluid, of which one or two spoonfuls added to boiling water will make an excellent cup of tea in a very short time. When prepared in a tea-pot, the water should be put in first and the requisite quantity of essence added afterwards; the flavor will be pronounced, coming out remarkably well in the liquor. This essence, when pure and properly made, will keep for any length of time in any climate on land or sea.
New Beverages—An effervescent wine may be produced from tea by forcing carbonic acid gas into the plain liquor as ordinarily prepared, and another beverage is produced by the introduction of an effervescing wine to the liquor only. While a pleasing drink is also prepared by treating the ordinary infusion with a little yeast and sugar, a tea-wine being produced from it differing in color and flavor according to the proportions in which the constituents are combined. Still another being evolved from this by the addition of a little alcohol to the compound. A drink called Rohrer or “tea spirit” is again produced by adding either whisky or brandy to the plain infusion when fresh made.
Paraguayan Tea—Is prepared in a filter or perforated bowl, known as a Maté, heated with warm water. A thin layer of sugar is first put in and a layer of leaves laid on top, another layer of sugar being added, the leaves being sandwiched between. The vessel is next filled with boiling water, which is allowed to percolate through the leaves and sugar. Before serving it is again sweetened with sugar until it becomes almost syrupy in substance, and frequently flavored with cinnamon, orange or lemon juice. Goat’s milk is often used instead of water, when thus prepared the infusion becomes ambrosial, approaching to that of “Chocolate Italienne” or nectar in flavor, becoming still more palatable when cold, but if allowed to stand too long exposed to the influence of the atmosphere it gets muddy and sours quickly.
CHAPTER VIII.
CHEMICAL, MEDICAL
AND
DIETICAL PROPERTIES.
Tea in chemistry is a complex mixture of a variety of substances, including Theine, Tannin, Dextrine, Glucose, Gum and an essential oil known as Volatile, which, together with a portion of the ash, pass into the solution when tea is infused. Being a leaf it also contains some woody fibre, the quantity of which as determined by Mulder, ranges from 17.1 in Green to 28.3 per cent. in Black teas. According to Peligot, whose admirable investigation of tea ranks as a chemical classic, it also contains a large quantity of legumen, a nitrogenous substance, sometimes termed vegetable Caseine, the percentage of which, as given by Peligot, is about 15 per cent. in tea in its usual commercial state. The woody fibre, legumen, some tannin coloring-matter and a certain quantity of the ash make up mainly the portion of the leaf which is not soluble in boiling water. In its commercial state tea is not subject to much irregularity in a hygrometric condition, there being only about 8 per cent. of moisture in it, which may fall to 6 or rise to 10 per cent. from outside causes.
Tea has been analyzed by many other chemists, but owing to a difference in the variety, character, quality, age, color and methods of preparation of the specimens submitted, the results have been as varied. The average composition in parts range as follows:—
| Chemical Constituents. | Quantities. | |
| Theine, | 3 | |
| Tannin, | 25 | |
| Volatile Oil, | 1 | |
| Albuminoids, | 15 | |
| Mineral Matter, | 6 | |
| Gum and Glucose, | 21 | |
| Vegetable Fibre, | 20 | |
| Fatty Substances, | 4 | |
| Water of Absorption, | 5 | |
| ——— | ||
| Total, | 100 | |
Theine—Is the alkaloid of tea and is the substance to which it owes its refreshing and stimulating properties. It is a crystallizable matter, soluble in water, very bitter to the taste and characteristic alike of both tea and coffee, being to these beverages what quinine is to bark, and with the base of cocoa which has recently received the name of “theobromine,” it is also closely related. It is further remarkable as occurring in many other plants dissimilar in structure and character, grown in remote countries, but yet selected by the inhabitants on account of their yielding a slightly exciting and refreshing beverage, and to the presence of which the peculiar physiological action of tea on the animal economy is attributed. It was first discovered under the name of Caffeine by Runge, who originally found it in Coffee, and later by Oudry, who extracted an identical substance from tea, to which he gave the name of Theine. Strickler subsequently produced it from cocoa, naming it Theobromine. These bodies are evidently related to uric acid as like it, when exposed to the action of nitric acid and ammonia they yield a purple coloring matter, technically termed murioxide.
Theine is a substance which crystallizes very beautifully, forming white, silk-like crystals containing an atom of water of crystallization, the specific gravity of which is 1.23 at 1°C., and the 9 water of crystallization is not altogether evaporated by a temperature of 150°. As deposited from aqueous solutions it still contains an atom of water, but as deposited from solutions in alcohol or ether, or when sublimed it is anhydrous. It is much more soluble in hot than cold water or in alcohol or ether, and according to Peligot, one part of theine dissolves in 300 parts ether or in 93 parts water at ordinary temperatures. It is a base of the same class as aniline and urea, that is to say, it will combine with acids yielding crystalline compounds, but never neutralizing an acid. With chloride of platinum, chloride of gold and corrosive sublimate, the hydrochlorate of theine enters into combination, forming a double salt with each. As will be manifest from its formula—C8—H10—N4O2—theine is one of the most highly nitrogenous substances known to chemists, and connected with this high percentage of nitrogen (almost double that formed in any other albuminous substance) is its property of yielding an abundance of cyanides when fused with soda lime, which property distinguishes it from a number of organic bases, such as piperine, morphine, quinine and cinchonine. With the base of cocoa—which has received the name of theobromine—theine is also closely related, being nothing more than methylated theobromine. Strecker having produced it from theobromine by acting upon a silver derivative with iodide of methyl, in a sealed tube heated at 100°. Theine exists in tea, not in the free state, but in the form of tannate of tea, which appears to be dissolved by the excess of tannic acid contained by the tea leaf, and so it happens that the theine makes its appearance in the infusion instead of remaining in the exhausted leaves. The proportion of theine in tea has been variously given by different chemists. Mulder finding 0.43 per cent. in Green tea and 0.46 in Black, while Stenhouse found 1.05 and 1.27 in Green and Black respectively. Peligot found 2.34 and 3.0, and Zoller, whose research is comparatively recent, found 3.94 per cent. of theine in India tea. But it would be a mistake to regard these varying results as showing that the quantity of theine in tea is variable, as they serve only to illustrate the difficulties which stand in the way of a quantitative extraction of the theine, and the imperfection of the earlier methods. In Peligot’s paper, these difficulties are referred to, and by making an attempt to extract the theine from a sample of tea the chemist acquires a sense of the truth of them. The experiments of the latter, however, being of great interest to chemists merits a somewhat detailed description. He began by determining the total amount of nitrogen contained in the dried leaves of different kinds of China tea at 110°, finding 6.15 per cent. in 100 parts of Oolong, 6.58 in Congou, and 6.30 in Green tea, while from one sample of India he extracted only 5.10 per cent., proportions six times greater than had been heretofore obtained by any previous analysis. Next testing every soluble substance for nitrogenous matter, he proceeded by successive eliminations to ascertain the quantity of theine in 27 other different samples and found that Green teas contained on an average 10 per cent. of water, and Black only 8 per cent., and also that the latter contained about 43.2 of matter soluble in boiling water while the former averaged as high as 47.1, and that this soluble matter yielded only 4.35 of nitrogen in Black teas, and 4.70 per cent. in Green. It remaining to be determined whether this large percentage of nitrogen was wholly due to the theine or in part to some other principle, he next found that the precipitate with sub-acetate of lead contained no apparent quantity, and then testing the theine by a modification of Mulder’s process obtained from Green tea an average of 2.48 per cent., and from a mixture of Green and Black 2.70. But greatly as these quantities exceed those of all other chemists, they were still unable to account for the whole amount of nitrogen found in the infusion, so by adding mere acetate of lead and ammonia, separating them by filtration, and passing through it a current of sulphuretted hydrogen to precipitate the lead, and evaporating the liquid with a gentle heat he obtained an abundant supply of crystals of theine. This supply he still further increased by re-evaporation until the whole amounted to 3.48 per cent. of the entire. There still remaining a syrup containing some theine it was precipitated with tannic acid, the result being added to that already crystallized it yielded a total of 5.84 from Green tea in the natural state and 6.21 in the dried leaf. These experiments being further continued by boiling the exhausted leaves with potash, it showed a presence of caseine to the extent of 28 per cent. of the mass, the proportion of the latter substance in the raw leaf being only 14 to 15.
Theine is extracted from tea by boiling a quantity of the leaves in a considerably larger quantity of distilled water and the liquor squeezed out of the leaves which are to be boiled with a fresh quantity of water and again subjected to pressure, the process being repeated a third time. The several portions of the infusion expressed from the leaves are put in the same vessel, mixed together thoroughly and treated with an excess of acetate of lead and ammonia, which precipitates the tannin and coloring matter. The liquor is next filtered and the filtrate evaporated down to a small bulk, first over a naked flame and afterwards in a water bath, and on being allowed to cool the solution will deposit crude theine which is removed by filtration, and the filtration nearly dried up in the water bath, and the residue boiled with alcohol, which dissolves the theine out of it. From this hot alcoholic solution theine crystallizes on cooling, a final purification being effected by crystallization from ether and decolorizing with animal charcoal. A simpler but less effective method is to place the dust of finely powdered tea-leaves, or an evaporated watery extract on a watch glass and cover it with a paper cone and hold it over a spirit lamp or gas jet the vapor arising from the glass condenses on the interior of the cone and forms small crystals of theine. Concentrated sulphuric acid dissolves theine in the cold without the production of color, but if the alkaloid be treated with nitric acid evaporated to dryness, and the reddish-yellow residue moistened with a little ammonia it turns a splendid purple color. Again, if a solution of theine be evaporated with chlorine on a watch glass a reddish-brown residue is obtained, which if again treated with the vapor of ammonia it becomes a deep violet of which the chief precipitants will be phosphoric acid, iodine and platinum, forming a yellow and brown precipitate respectively.
Theine having no odor and only a slightly bitter taste it obviously has very little to do with the flavor of tea. It is, however, considered a very valuable constituent on account of the large percentage of nitrogen which it contains and to which is attributed the peculiar physiological action of tea on the animal economy, but what changes it undergoes in the human system has not yet been determined. When oxydized artificially it decomposes into methleamic (hydrocyanic) acid, a nitrogenous compound closely allied to caseine or gluten, and as hot water extracts but very little of this substance a large amount of it is wasted in the ordinary infusion, which might otherwise be saved by the addition of a little carbonate of soda to the water in preparing it.
Tannin—A large portion of the Tea-extract consists of tannin (tannic acid of a peculiar kind), there being much more in Green teas than in Black, ranging from 13 to 20 per cent. in the former, and 8 to 12 per cent. in the latter, but averaging 12 and 9.50 per cent. respectively, the difference being due to the fact that part of the tannin originally existing in the raw-leaf is destroyed during the process of fermentation to which Black teas are subjected in manipulation. It is a powerful astringent principle, puckering up the mouth when chewed, and to which tea owes its bitterness when overdrawn or boiled, constipating effect on the bowels, and the inky-black color which it imparts to water containing salts-of-iron. But whether it contributes in any degree to the exhilarating, satisfying or narcotic action of the tea has not yet been determined. Johnston thinks it probable that it does exert some such effect from the fact that a species of tannin is found in the Betel-nut, which when chewed produces a mild form of intoxication, but as to whether this property assists or retards digestion is still an unsettled question, the old maxim, “what is one man’s meat is another man’s poison,” being particularly true of this substance. Many persons finding that the use of tea while eating, or immediately after eating, has a soothing effect on their system, while the same persons after drinking coffee, under like circumstances, get nervous, and cannot digest their food properly. As there is no tannin in coffee, it stands to reason that the substance must have some influence on the digestive organs.
For the estimation of tannin in tea various processes are in use, a tritration by means of a standard solution of gelatine, which depends upon the well-known property possessed by gelatine of forming insoluble compounds with tannin being the most effective, but tedious and difficult. A much more simple and promising method consists in tritrating by means of a standard solution of lead, the point of saturation being indicated by the red color struck by an ammoniacal solution of ferricyanide of potassium, one drop of this solution being capable of coloring one milligram of tannin dissolved in 100 parts of water, the exact strength of the solution of lead being ascertained with a standard solution of tannin. In using the solution of lead, 10 drops of it are first diluted with 9 times its volume in water, and the tea infusion dropped into it from a graduated burette until the indicator strikes a red with the drop of the indicator. The infusion of tea is made by boiling 2 grains of the leaves in water and afterwards diluting it to 250, it being understood that the smaller the quantity of this infusion required to saturate the 10 parts of the lead solution, the higher the percentage of tannin in the sample of tea treated. This test is specially applicable for ascertaining whether Black tea in particular has been mixed with spent leaves. By taking the normal percentage of tannin in pure Black tea at 10 and the percentage of tannin in spent tea as 2, the difference is the extent of adulteration.
There is a great variability in the amount of tannin contained in the different varieties of tea, varying in quantity according to the country of production, kind, quality, and state of growth when picked. In six samples of China Oolong teas recently tested, the percentage of tannin extracted, after an infusion of thirty minutes, averaged only 7.44, an almost similar result being obtained from an examination of the finest Congou-China Green teas, ranging from 11.87 to 14.11 per cent., some Japan samples under the same conditions yielding on an average from 8 to 10. While with a sample of the finest Assam (India) a percentage of 17.73 of tannin by actual weight was extracted after an infusion of only fifteen minutes, two samples of India and Ceylon giving respectively 18.91 and 15.26, proving conclusively that India and Ceylon teas are much more heavily weighted with tannin than China and Japan teas. The percentage of tannin in the extract is also quite irregular, according to the quality of the tea, the ratio of tannin to the extract varying quite uniformly with the value of the tea, the percentage falling and rising with the percentage of the extract and cost of the tea.
Volatile Oil—Is the principle which imparts to tea its peculiar flavor and aroma, and upon the amount contained in the dried leaves depends the strength and pungency of the infusion. It is present only in very small quantities, but is, nevertheless, very potent in its effects, the proportions ranging, according to Mulder, from 0.6 per cent. in Black tea to 0.80 in Green, but averaging 0.75 in all good teas. It is found by distilling the tea with water, is lighter in body than water, citron-yellow in color, resinifying on exposure, solidifying with cold, and exerting a powerfully exciting or stimulating effect on the system. But there being no chemical analysis of this constituent extant, its exact effect on the human system is difficult to define. By some authorities it is claimed to produce wakefulness, acting, it is said, in the same manner as digitalis (fox-glove) which, when taken in overdoses, causes anxiety and inability to sleep. It is a well-known fact that Green teas produce these effects, while Black does not, the excessive fermentation to which the latter are subjected in the process of curing, dissipating the volatile oil to a greater extent, or, more properly, altering its general character not only in effect but also in flavor.
Gum or Gluten—If it is necessary to estimate the quantity of gum or gluten in tea, as sometimes happens, evaporate an aqueous decoction of the leaves to an extract, and treat the residue with methylated spirit, filter and wash off with hot water, after which evaporate the solution to dryness, next weighing and burning it to an ash and deduct the mineral residue from the original weight of the leaves. Tea extract also yields a large quantity of ammonia when boiled with potash, and it is probable that this character may prove valuable also in testing the genuineness of tea. Tea leaves under an extraordinary amount of ammonia, when submitted to this test, are found to be remarkably rich in nitrogen, the determination of which is also a means of identification. It may also be here remarked that when tea-leaves have been exhausted by infusion, alcohol is still capable of extracting a considerable amount of soluble matter. This alcohol extract, when infused in boiling water, furnishes a liquor which smells and tastes strongly of tea, which, were it not for the expense of the solvent and trouble attending its separation, could no doubt be profitably employed. A fixed oil composed of equal parts of oleine and stearine, serving many purposes, medicinal, illuminating and others, is extracted from the seeds of the tea-plant in many parts of China and Tartary. The other substances extracted from the tea-leaf consists principally of those which, in various proportions, enter into the composition of all plants and include a modification of constituents analagous to sugar, fat, salts, starch and water. The fibre, tannin, legumen coloring matter and a certain quantity of ash making up mainly the portion of the leaf insoluble in boiling water.