The Project Gutenberg eBook of All About Coffee, by William H. Ukers.

John Cotton Dana, of the Newark Public Library, says he remembers how in his old home in Woodstock, Vt., they had always, in the attic, a big stone jar of green coffee. This was sacred to the great feast days, Thanksgiving, Christmas, etc. Just before those anniversaries, the jar was brought forward and the proper amount of coffee was taken out and roasted in a flat sheet-iron pan on the top of the stove, being stirred constantly and watched with great care. "As my memory seems to say that this was not constantly done," says Mr. Dana, "it would seem that, even then, my father, who kept the general store in the village, bought roasted coffee in Boston or New York."

At the close of the century, there were still many advocates of boiling coffee; but although the coffee trade was not quite ready to declare its absolute independence in this direction, there were many leaders who boldly proclaimed their freedom from the old prejudice. Arthur Gray, in his Over the Black Coffee, as late as 1902, quoted "the largest coffee importing house in the United States" as advocating the use of eggs and egg-shells and boiling the mixture for ten minutes.

Better coffee making by co-operative trade effort got its initial stimulus at the 1912 convention of the National Coffee Roasters Association. As a result of discussions at that meeting and thereafter, a Better Coffee Making Committee was created for investigation and research.

The coffee trade's declaration of independence in the matter of boiled coffee was made at the 1913 convention of the National Coffee Roasters Association, when, after hearing the report of the Better Coffee Making Committee, presented by Edward Aborn of New York, it adopted a resolution saying that the recommendations met with its approval and ordering that they be printed and circulated.

The work done by the committee included "the first chemical analysis of brewed coffee on record", a study of grindings, and a comparison of the results of four brewing methods. Its conclusions and recommendations were embodied in a booklet published by the National Coffee Roasters Association, entitled From Tree to Cup with Coffee, and were as follows:

Roasting

The Roaster or "Coffee Chef" is the only cook necessary to a good cup of coffee. He sends it to the consumer a completely cooked product.

In the roasting process the berries swell up by the liberation of gases within their substance. The aromatic oils contained in the cells are sufficiently developed or "cooked", and made ready for instantaneous solution with boiling water, when the cells are thoroughly opened by grinding.

The roasting principles of different green coffees vary. Trained study and a nice science in timing the roast and manipulating the fire is necessary to a perfect development of aroma and flavor.

The drinking quality is largely dependent upon the experienced knowledge of the coffee roaster and his scientific methods and modern machinery, by which the coffee is not only roasted, but cleaned, milled and completely manufactured to a high point of perfection.

In their National Association work, the wholesale roasters are giving the public new facts and valuable information, from scientific researches, investigations, etc.

Grinding. The roasted berry is constructed of fibrous tissues formed into tiny cells visible only under the microscope, which are the "packages" wherein are stored the whole value of coffee, the aromatic oils. Like cutting open an orange, the grinding of coffee is the opening of surrounding tissue and pulp, and the finer it is cut the more easily are the "juices" released.

The fibrous tissue itself is waste material, yielding, by boiling or too long percolations, a coffee colored liquid which is fibrous and twangy in taste, has no aromatic character, and contains undesirable elements.

The true strength and flavor of roasted coffee is ground out, not boiled out. The finer coffee is ground, the more thoroughly are the cells opened, the surfaces multiplied, and the aromatic oils made ready for separation from their husks. Hence it follows that:

Coarse ground coffee is unopened coffee—coffee thrown away.

The finer the grind, the better and greater the yield. With pulverized coffee (fine as corn meal) the fully released aromatic oils are instantaneously soluble with boiling water.

In ground coffee the oils are standing in "open packages," escaping into the air and absorbing moisture, etc., necessitating quick use or confinement in air proof and moisture proof protection.

Brewing. From scientific researches by the National Coffee Roasters' Association, including the first chemical analysis on record of brewed coffee, produced by various brewing methods, the fundamental principles of coffee making have been clearly established. These principles are simple, and when once understood equip any person to intelligently judge the merits and defects of the various coffee making devices on the market. They constitute the law of coffee brewing, and may be stated as follows:

Correct brewing is not "cooking." It is a process of extraction of the already cooked aromatic oils from the surrounding fibrous tissue, which has no drinkable value. Boiling or stewing cooks in the fibre, which should be wholly discarded as dregs, and damages the flavor and purity of the liquid. Boiling coffee and water together is ruin and waste.

The aromatic oils, constituting the whole true flavor, are extracted instantly by boiling water when the cells are thoroughly opened by fine grinding. The undesirable elements, being less quickly soluble, are left in the grounds in a quick contact of water and coffee. The coarser the grind the less accessible are the oils to the water, thus the inability to get out the strength from coffee not finely enough ground.

Too long contact of water and coffee causes twang and bitterness, and the finer the grind the less the contact should be. The infusion, when brewed, is injured by being boiled or overheated. It is also damaged by being chilled, which breaks the fusion of oils and water. It should be served immediately, or kept hot, as in a double boiler.

Tests show that water under the boiling point, 212°, is inefficient for coffee brewing, and does not extract the aromatic oils [378]. Used under this temperature, it is a sure cause of weak and insipid flavor. The effort to make up this deficiency by longer contact of coffee and water, or repeated pouring through, results in no extraction of the oils, but draws out undesirable elements, such as coffee-tannin, which is soluble in water at any temperature and is governed by the time of contact.

Coffee-tannin, which is not the commercial tannic acid, is eliminated to practically nothing in the quick brewing methods.

The chemical analysis of brewed coffee shows the following:

	Coffee Tannin per Cup	Comparative Proportions
Percolator method, [379] fine gran. 5 minutes' steeping	2.90 grains	—————
Boiling Method, medium gran.	2.35 grains	————
Steeping Method, medium gran.	2.31 grains	———
Filtration (or Drip) Method Pulverized	0.29 grains	—

Brewing is the final manufacturing process of coffee. All previous perfection is dependent upon it. Like food products which lose nutritive value by bad cooking, coffee loses its best values by wrong brewing. Brewed by the very simple correct methods, it is an unfailingly clear, fragrant, taste-charming beverage, universally loved and scientifically approved.

The committee made a further report in 1914, and some of the findings were subsequently published in an association booklet called The Coffee Book, used in connection with the second National Coffee Week campaign in 1915. In it were these:

Also, the committee emphasized its previous findings, particularly this one: "Filter bags should be kept in cold water when not in use. Drying causes decomposition. Keeps sweet if kept wet. Use muslin for filter bag and pulverized granulation."

The association brought out this same year, on recommendation of the committee, its Home coffee mill, an "ideal and standard coffee mill for home use." It was a wall mill equipped with a glass-front metal hopper and employing a ratchet spring-lock nut and double-action grinders. The mill was later improved with an all-glass hopper and a tumbler bracket. More than 20,000 of these mills have been sold.

At the suggestion of the author, the efficiency of nine different coffee-making devices (including boiling and drip pots, pumping percolators, cloth and paper filters) was investigated in the laboratories of the Mellon Institute of Industrial Research of the University of Pittsburgh in 1915; and Dr. Raymond F. Bacon submitted a report that showed that the boiling method produced the highest percentage of caffetannic acid and caffein; the French drip process the lowest. The investigation disclosed also a more palatable brew at 195° to 200° F. than at the boiling point.

Another notable contribution to the science of coffee brewing was made by the Home Economics Laboratories of the University of Kansas in 1916. The experiments extended over one year. They showed that strength and color in coffee brews are independent of blend and price and are most fully obtained by pulverized granulation, which was found to be the most efficient; that the consumer pays for flavor and that filtration yielded the best brew. The French drip, or true percolator, did not figure in these experiments.

At the 1915 convention of the National Coffee Roasters Association, Mr. Aborn reported that 4,000 copies of the committee's findings on grinding and brewing had been given away: and the facts were further circulated in 2,000,000 booklets issued during two years. He told of tests which showed that while there might be reasons of commercial expediency for packing ground coffee, it could not be defended as a quality principle; also that plate-grinders produced a more efficient drawing granulation than roller grinders, and that the idea that the steel-cut process eliminates dirt was an absurdity, as "the finest ground coffee is not dirt but coffee in its most efficient drawing condition." He added, "I have paid no attention to chaff removal in these tests as the uselessness of such removal has been repeatedly shown up." The reference here was to his 1914 and 1913 reports, in which it was stated that "removing the chaff in the steel-cut process does not remove any of the tannin, and for this purpose the steel-cut process is wholely futile, and a wasteful and unnecessary tax upon cost", and that "the removal of the chaff appreciably affects the flavor and depreciates the cup value."

This report repeated previous findings against the pumping percolator as producing an inefficient brew and being a very faulty utensil. Mr. Aborn concluded his report by saying:

The old time boiling method has fewer and fewer defenders and holds its own only as a superstition. I therefore pass it over as a discarded issue.... It is but repetition of former reports for me to say that pulverized granulation is the most efficient granulation; that it assures the highest quality of brew and the lowest proportion of coffee to a given strength; that it is the most saving and most satisfying grinding for all to use; that it (the coffee) must be fresh ground; that the filtration method is the most correct in fundamental principles and that used with a muslin bag it assures the consumer coffee of the purest, finest flavored quality, highest health value and sure economy.

The campaign of education was continued during 1916, producing encouraging results among schools, colleges, the medical fraternity, newspapers, with the trade and the consumer. It marked the first big constructive work combining the practical and scientific phases of grinding and brewing methods. In his report at the 1916 convention of the National Coffee Roasters Association, Mr. Aborn reviewed the four years work, and pointed out what had been accomplished. He told of a new booklet, to be called the True Book on Coffee Grinding and Brewing, and an educational exhibit box for schools about to be issued. Due to opposition which developed from trade interests that were putting out steel-cut and other grinds of coffee not favored by the committee, and also because many members thought the association should not exploit any particular method of grinding or brewing, it was decided to make no further publication of the coffee grinding and brewing conclusions of the committee until they had been confirmed by laboratory research.

Boiling and filtration tests in the mountains of the Yellowstone Park by W.H. Aborn in 1916 showed that the limit of coffee brewing was reached at an altitude of nine thousand feet.

At the 1916 meeting, Dr. Floyd W. Robison of the Detroit Testing Laboratories, read a notable paper entitled "What do we know about coffee?," which hailed coffee as a food product, warned the roasters to beware of half-facts, and urged the importance of a research laboratory. It was published and given distribution by the association.

The educational exhibit box showing samples of coffee from plantation to cup, including five different grinds, was issued in 1917, and sold for one dollar.

The Better Coffee Making Committee also published in this year a booklet entitled Coffee Grinding and Brewing in which it summarized its work to date, and presented its special plea for cotton-cloth filters as the ideal coffee-making device.

This booklet aroused considerable discussion, particularly between those who favored the paper filter and those who, with Mr. Aborn, believed cotton cloth, such as muslin, to be the most efficient strainer. "Cotton", argued Mr. Aborn, "is an ideal sanitary strainer because it contains no chemical or questionable manufacturing element."

It was pointed out by Dr. Floyd W. Robison that while cotton cloth, such as muslin, does give a fairly clear coffee, it is not so clear as by the methods where a filter paper is used. He said:

Both methods have serious objectionable features. The muslin bag, particularly, is decidedly unsanitary, especially when used in restaurants and hotels. It is rarely kept clean, and one who has frequented restaurants and many hotel kitchens knows that it lends itself to very unclean and unsightly methods of handling. The food inspector has to check this up perhaps as often as any one feature about a restaurant.

The objection to the filter paper is not at all on the ground of sanitation. It is ideal in this respect. The claim is made, and at least, in part, substantiated, that it does hold back valuable features of the brew.

There are many points about the filter that have not been considered at all. Mr. Calkin believes that the very best type of filter is a bed of coffee itself, and I must say this has the sanction of good laboratory experience.

It is a known fact that the fats in coffee are very dense and represent twelve to fifteen percent of the coffee weight. These fats—due to the simplest chemical action of contact with air, moisture and continued heat—begin a fermentation in the completed beverage. In the cloth-filtering process—due to the rapid passage of water through grounds almost as quickly as poured—the largest percentage of fats is carried into the beverage. Fat being lighter than water rises to the top of water if given a certain amount of time during the brewing process. Were there no fats (which ferment) in coffee there would be no need for placing cloth-filtering material under water, as suggested, to keep them from becoming sour.

In the booklet referred to, Mr. Aborn expressed himself as follows on the filtration method:

The filtration method is not new, but well tried, thoroughly proven and long used, though often incorrectly. It is the method followed, more or less correctly, by all of the first-class hotels in the world. It is controlled by no patent or proprietary device, and requires a most inexpensive equipment. For a perfect result it but demands an accurate adherence to simple but vital principles. Deviations from these fundamentals, though apparently slight, cause failure. When they, and the necessary exact following of them, are clearly understood, any person, even a small child, can brew coffee with unvarying success.

The first point to consider in filtration is the dimensions of the filter bag, or container of the ground coffee, in relation to the quantity of coffee used and the granulation of same. If the filter be a muslin bag, free on all sides, the filtering surface is considerable and permits the necessary quick passage of water through the grounds, provided the bag is of a wide enough diameter as to prevent too great a depth of grounds through which the water cannot quickly penetrate. The error of too narrow a filter is a common one. It causes a delayed filtration, which means undesirably long contact of water and coffee and also the cooling of the liquid which in a correct, undelayed filtration is smoking hot at completion. The bag should also not be too long or be allowed to hang or soak in the liquid. A filter bag set tightly into a pot against its sides, thus surrounded with impenetrable walls, is greatly reduced in filtering surface, and the filtration is thereby slackened.

The filter material should not be too coarse in texture, like cheese cloth, or too heavy and impenetrable, like very heavy muslin. A moderate weight muslin, not too light, is efficient.

The degree of granulation also, of course, affects the rate of flow. The coarser the grind the faster the flow, which permits a larger quantity of coffee to a given diameter of filter bag.

A most frequent fault in the use of the filtration method is the failure to understand the fine degree of grinding necessary to the best results. When the grind is not sufficiently fine the extraction is, of course, weak. A fine grind (like fine cornmeal) is essential. It does not retard the flow if the filter is of right dimensions. A powdered grind (like flour) is so fine that it is apt to "mat" itself into a resisting floor.

Many users of the filtration method pour the liquid through more than once. This gains some added color, but adds undesirable element, depreciates flavor and is especially inadvisable when the grind is sufficiently fine. One pouring only is recommended for the best results.

The chinaware, or glazed earthenware pot, sometimes called the French drip pot, with a chinaware or earthenware sieve container for the grounds at the top through which the water is poured, being free of all metal, is inviting in purity and in hygienic merit. Together with the filter bag, it is subject to the above remarks on dimensions. A chinaware sieve cannot be made as fine as a metal sieve and cannot of course hold very fine granulation as can cotton cloth. More coffee for a given strength is, therefore, required. The upper container should be wide enough, for a given quantity of coffee, as to allow an unretarded flow, and the more openings the strainer contains the better.

In any drip, filtration or percolating method the stirring of the grounds causes an over-contact of water and coffee and results in an overdrawn liquor of injured flavor. If the water does not pass through the grounds readily, the fault is as above indicated and cannot be corrected by stirring or agitation. Many complaints of bitter taste are traced to this error in the use of the filtration method.

It is not necessary to pour on the water in driblets. The water may be poured slowly, but the grounds should be kept well covered. The weight of the water helps the flow downward through the grounds. Care should be taken to keep up the temperature of the water. Set the kettle back on the stove when not pouring. If the water is measured, use a small heated vessel, which fill and empty quickly without allowing the water to cool.

In 1917, The Tea and Coffee Trade Journal made a comparative coffee-brewing test with a regulation coffee pot for boiling, a pumping percolator, a double glass filtration device, a cloth-filter device, and a paper filter device. The cup tests were made by E.M. Frankel, Ph.D.; and William B. Harris, coffee expert, United States Department of Agriculture. The brews were judged for color, flavor (palatability, smoothness), body (richness), and aroma. The test showed that the paper filtration device produced the most superior brew. The cloth-filter, glass-filter, percolator, and boiling pot followed in the order named.

At the 1917 convention of the National Coffee Roasters Association, John E. King, of Detroit, announced that laboratory research which he had had conducted for him showed that the finer the grind, the greater the loss of aroma, and so he had selected a grind containing ninety percent of very fine coffee and ten percent of a coarser nature, which seemed to retain the aroma. He subsequently secured a United States patent for this grind. Mr. King announced also at this meeting that his investigations showed there was more than a strong likelihood that the much-discussed caffetannic acid did not exist in coffee—that it most probably was a mixture of chlorogenic and and coffalic acids.

The World War operated to interfere with the coffee roasters' plans for a research bureau; and in the meantime the Brazil planters, in 1919, started their million-dollar advertising campaign in the United States, co-operating with a joint committee representing the green and roasted coffee interests. In the following year (June, 1920), this committee arranged with the Massachusetts Institute of Technology to start scientific research work on coffee, the literature of the roasters' Better Coffee Making Committee being turned over to it; and the Institute began to "test the results of the committee's work by purely analytical methods."

The first report on the research work at the Massachusetts Institute of Technology was made by Professor S.C. Prescott to the Joint Coffee Trade Publicity Committee in April, 1921. The committee gave out a statement saying that Prof. Prescott's report stated that "caffein, the most characteristic principle of coffee, is, in the moderate quantities consumed by the average coffee drinker, a safe stimulant without harmful after-effects."

There was no publication of experimental results; but the announced findings were, in the main, a confirmation of the results of previous workers, particularly of Hollingworth, with whose statement, that "caffein, when taken with food in moderate amount is not in the least deleterious," the report was quoted as being in entire agreement.

At the annual convention of the National Coffee Roasters Association, November 2, 1921, Professor Prescott made a further report, in which he stated that investigations on coffee brewing had disclosed that coffee made with water between 185° and 200° was to be preferred to coffee made with the water at actual boiling temperature (212°), that the chemical action was far less vigorous, and that the resulting infusion retained all the fine flavors and was freer from certain bitter or astringent flavors than that made at the higher temperature. Professor Prescott announced also that the best materials for coffee-making utensils were glass (including agate-ware, vitrified ware, porcelain, etc.), aluminum, nickel or silver plate, copper, and tin plate, in the order named [381].

The Joint Coffee Trade Publicity Committee's booklet on Coffee and Coffee Making, issued in 1921, was very guarded in its observations on grinding and brewing. It avoided all controversial points, but it did go so far as to say on the general subject of brewing:

Chemists have analyzed the coffee bean and told us that the only part of it which should go into our coffee cups for drinking is an aromatic oil. This aromatic element is extracted most efficiently only by fresh boiling water. The practice of soaking the grounds in cold water, therefore, is to be condemned. It is a mistake also to let the water and the grounds boil together after the real coffee flavor is once extracted. This extraction takes place very quickly, especially when the coffee is ground fine. The coarser the granulation the longer it is necessary to let the grounds remain in contact with the boiling water. Remember that flavor, the only flavor worth having, is extracted by the short contact of boiling water and coffee grounds and that after this flavor is extracted, the coffee grounds become valueless dregs.

The report contained also the following helpful generalities on coffee service and the various methods of brewing in more or less common use in the United States in 1921:

Although the above rules are absolutely fundamental to good Coffee Making, their importance is so little appreciated that in some households the lifeless grounds from the breakfast Coffee are left in the pot and resteeped for the next meal, with the addition of a small quantity of fresh coffee. Used coffee grounds are of no more value in coffee making than ashes are in kindling a fire.

After the coffee is brewed the true coffee flavor, now extracted from the bean, should be guarded carefully. When the brewed liquid is left on the fire or overheated this flavor is cooked away and the whole character of the beverage is changed. It is just as fatal to let the brew grow cold. If possible, coffee should be served as soon as it is made. If service is delayed, it should be kept hot but not overheated. For this purpose careful cooks prefer a double boiler over a slow flre. The cups should be warmed beforehand, and the same is true of a serving pot, if one is used. Brewed coffee, once injured by cooling, cannot be restored by reheating.

Unsatisfactory results in coffee brewing frequently can be traced to a lack of care in keeping utensils clean. The fact that the coffee pot is used only for coffee making is no excuse for setting it away with a hasty rinse. Coffee making utensils should be cleansed after each using with scrupulous care. If a percolator is used pay special attention to the small tube through which the hot water rises to spray over the grounds. This should be scrubbed with the wire-handled brush that comes for the purpose.

In cleansing drip or filter bags use cool water. Hot water "cooks in" the coffee stains. After the bag is rinsed keep it submerged in cool water until time to use it again. Never let it dry. This treatment protects the cloth from the germs in the air which cause souring. New filter bags should be washed before using to remove the starch or sizing.

Drip (or Filter) Coffee. The principle behind this method is the quick contact of water at full boiling point with coffee ground as fine as it is practical to use it. The filtering medium may be of cloth or paper, or perforated chinaware or metal. The fineness of the grind should be regulated by the nature of the filtering medium, the grains being large enough not to slip through the perforations.

The amount of ground coffee to use may vary from a heaping teaspoonful to a rounded tablespoonful for each cup of coffee desired, depending upon the granulation, the kind of apparatus used and individual taste. A general rule is the finer the grind the smaller the amount of dry coffee required.

The most satisfactory grind for a cloth drip bag has the consistency of powdered sugar and shows a slight grit when rubbed between thumb and finger. Unbleached muslin makes the best bag for this granulation. For dripping coffee reduced to a powder, as fine as flour or confectioner's sugar, use a bag of canton flannel with the fuzzy side in. Powdered coffee, however, requires careful manipulation and cannot be recommended for everyday household use.

Put the ground coffee in the bag or sieve. Bring fresh water to a full boil and pour it through the coffee at a steady, gradual rate of flow. If a cloth drip bag is used, with a very finely ground coffee, one pouring should be enough. No special pot or device is necessary. The liquid coffee may be dripped into any handy vessel or directly into the cups. Dripping into the coffee cups, however, is not to be recommended unless the dripper is moved from cup to cup so that no one cup will get more than its share of the first flow, which is the strongest and best.

The brew is complete when it drips from the grounds, and further cooking or "heating up" injures the quality. Therefore, since it is not necessary to put the brew over the fire, it is possible to make use of the hygienic advantages of a glassware, porcelain or earthenware serving pot.

Boiled (or Steeped) Coffee. For boiling (or steeping) use a medium grind. The recipe is a rounded tablespoonful for each cup of coffee desired or—as some cooks prefer to remember it—a tablespoonful for each cup and "one for the pot." Put the dry coffee in the pot and pour over it fresh water briskly boiling. Steep for five minutes or longer, according to taste, over a low fire. Settle with a dash of cold water or strain through muslin or cheesecloth and serve at once.

Percolated Coffee. Use a rounded tablespoonful of medium fine ground coffee to each cupful of water. The water may be poured into the percolator cold or at the boiling point. In the latter case, percolation begins at once. Let the water percolate over the grounds for five or ten minutes depending upon the intensity of the heat and the flavor desired.

In response to a request by the author, Charles W. Trigg has contributed the following discussion of coffee making:

Various Aspects of Scientific Coffee Brewing

Before converting it into the beverage form, coffee must be carefully selected and blended, and skillfully roasted, in order thus far to assure obtaining a maximum efficiency of results. No matter how accurately all this be done, improper brewing of the roasted bean will nullify the previous efforts and spoil the drink; for roasted coffee is a delicate material, very susceptible to deterioration and of doubtful worth as the source of a beverage unless properly handled.

There probably never was produced a drink which so fits into the exacting desires of the human appetite as does coffee. Properly prepared, it is a delightful beverage: but incorrectly made, it becomes an imposition upon the palates of mankind. Sensitive though coffee is to improper manipulation, the best procedure for brewing it is also the easiest. Cheap coffee well made excels good coffee poorly made.

Constituent Concepts. The roasting of green coffee causes an alteration in the constitution of its constituents, with the result that some of the compounds present therein which were originally water-soluble are rendered insoluble, and some which were insoluble are converted into soluble ones. A portion of the original caffein content is lost by sublimation. The aromatic conglomerate, caffeol, is formed, and a considerable quantity of gas is produced, a portion of which, developing pressure in the cells of the beans, pops, or swells, them so as to increase the size of each individual bean. The constituents which are water-soluble after the torrefaction may be generally classified as heavy extractives and light aromatic materials. The percentages and nature of these materials in the roasted coffee will vary with the type of coffee and with the roast which it is given. In general, and in particular for purposes of comparison of methods of brewing, they may be considered to be the same and to occur in about the same proportions in all coffees.

The heavy extractives are caffein, mineral matter, proteins, caramel and sugars, "caffetannic acid", and various organic materials of uncertain composition. Some fat will also be found in the average coffee brew, being present not by virtue of being water soluble, but because it has been melted from the bean by the hot water and carried along with the solution.

The caffein furnishes the stimulation for which coffee is generally consumed. It has only a slightly bitter taste, and because of the relatively small percentage in which it is present in a cup of coffee, does not contribute to the cup value. The mineral matter, together with certain decomposition and hydrolysis products of crude fiber and chlorogenic acid, contribute toward the astringency or bitterness of the cup. The proteins are present in such small quantity that their only rôle is to raise somewhat the almost negligible food value of a coffee infusion. The body, or what might be called the licorice-like character of coffee, is due to the presence of bodies of a glucosidic nature and to caramel.

As has been previously pointed out [382], the term "caffetannic acid" is a misnomer; for the substances which are called by this name are in all probability mainly coffalic and chlorogenic acids. Neither is a true tannin, and they evince but few of the characteristic reactions of tannic acid. Some neutral coffees will show as high a "caffetannic acid" content as other acid-charactered ones. Careful work by Warnier [383] showed the actual acidities of some East Indian coffees to vary from 0.013 to 0.033 percent. These figures may be taken as reliable examples of the true acid content of coffee, and though they seem very low, it is not at all incomprehensible that the acids which they indicate produce the acidity in a cup of coffee. They probably are mainly volatile organic acids together with other acidic-natured products of roasting.

We know that very small quantities of acid are readily detected in fruit juices and beer, and that variation in their percentages is quickly noticed, while the neutralization of this small amount of acidity leaves an insipid drink. Hence it seems quite likely that this small acid content gives to the coffee brew its essential acidity. A few minor experiments on neutralization have proven the production of a very insipid beverage by thus treating a coffee infusion. So that the acidity of certain coffees most apparently should be attributed to such compounds, rather than to the misnamed "caffetannic acid."

The light aromatic materials, and the other substances which are steam-distillable, i.e. which are driven off when coffee is concentrated by boiling, are the main determining factors in the individuality of coffees. These compounds, which are collectively called "caffeol", vary greatly in the percentages present in different coffees, and thus are largely responsible for our ability to distinguish coffees in the cup. It is these compounds which supply the pleasingly aromatic and appetizing odor to coffee.

All of these compounds, with the possible exception of the proteins, are easily soluble in both hot and cold water. The fact that a clear coffee extract made with hot water does not show any precipitate immediately upon cooling, proves that cold water will give as complete an extraction as hot water. However, speed of extraction is materially increased with rise in temperature, due to the fact that the rate and degree of solubility of the substances in water, and the diffusion of the water through the cell walls of the coffee, are accelerated. Also, the resistance which the fat content of the bean offers to the wetting of the coffee, and the persistency of the "enfleurage" action of the fat in retaining the caffeol, are less with hot than with cold water. Accordingly, the speed of extraction is increased by using hot water, and the efficiency of extraction procured per unit time of subjection to water is higher.

Prolonged contact of coffee with water results in the hydrolysis of some of the insoluble materials and subsequent extraction of the substances thus formed. The rate of hydrolysis also increases with temperature: and as these compounds are of an astringent or bitter nature, the solution obtained upon boiling coffee is naturally possessed of a flavor unpleasant to the palate of the connoisseur. Boiling of the coffee infusion after it has been removed from the grounds also has a deleterious effect, as the local overheating of the solution at the point of application of the heat results in a decomposition, particularly if the solution be converted into steam at this point, leaving a thin film of solids temporarily exposed to the destructive action of the heat. Some of the more delicate constituents are unfavorably affected by such treatment, and undergo hydrolysis and oxidation. The products thus formed are thrown into relief in the flavor by the loss of the aromatic properties through steam distillation which is incidental to boiling.

It is a well known fact that re-warming a coffee brew has a unfavorable effect upon it. This is probably due in part to a precipitation of some of the water-soluble proteins upon standing, and their subsequent decomposition when heat is applied directly to them in reheating the solution. The absorption of air by the solution upon cooling, with attendant oxidation, which is accentuated by the application of heat in re-warming, must also be considered, as well as the other effects of boiling as set forth, and the action of the materials of which the coffee pot is constructed upon the solution.

Physical Conception. The coffee bean is composed of a large number of cells which function as natural containers and retainers of coffee fat and of the aromatic flavoring substances. In order to render the soluble solids fully accessible, the resistance which these cells offer to the extracting water must be overcome by grinding so as to break open all of them. In this manner a grind is obtained which will give a maximum removal of the heavy extractives. But when all of the cells are broken, great opportunity is offered for the escape of the caffeol, which is further enhanced by the slight heating which usually accompanies such fine grinding. So much caffeol escapes that even our most expert cup-testers would experience difficulty in identifying powdered coffees in a blind test. What cup-testers, in fact, use powdered coffees for making their cup selections?

Consider powdered coffee, compared with freshly ground coffee of a coarser grind. Neither the former nor its brew possesses the amount of characteristic flavor or aroma, attributable to caffeol, evidenced by the latter. The explanation of this is that the finer the grind, the more readily accessible are the soluble constituents of the coffee to the extracting water. Caffeol, however, in addition to being water-soluble, is extremely fugacious, so that when the grinding is carried to such a fineness that every cell is broken, the greater part of the caffeol volatilizes before the water comes into contact with it. It is therefore highly desirable that a grind be used wherein all of the cells are not broken, but a grind that is sufficiently fine to permit efficient extraction. In the light of this knowledge, the grind advocated by King [384] seems to be logical, for with it—though neither a maximum of the non-volatile extractives nor a maximum of caffeol is obtained—an all-round maximum of cup quality is procured.

The escape, upon grinding, of these volatile aromatic and flavoring constituents which lend individuality to coffees, makes it essential that the roasted beans be ground immediately prior to extraction.

Different Methods of Extraction. The methods employed for preparing the coffee drink may be classified under the general headings of boiling, steeping, percolation, and filtration. True percolation is the simple process known by the trade as filtration; but in this classification, the term indicates the style of extraction exemplified by the pumping percolator.

Boiled coffee is usually cloudy, due to the suspension of fine particles resulting from the disintegration of the grounds by the violence of boiling. The usual procedure in clarifying the decoction is to add the white of an egg or some egg-shells, the albumen of which is coagulated upon the fine particles by the heat of the solution, and the particles thus weighted sink to the bottom. Even this procedure, requiring much attention, does not give as clear a solution as some of the other extraction procedures employed. The conditions to which coffee is subjected during boiling are the worst possible, as both grounds and solution undergo hydrolysis, oxidation, and local-overheating, while the caffeol is steam-distilled from the brew. Many persons, who have long been accustomed to drinking the relatively bitter beverage thus produced, are not satisfied by coffee made in any other way; but this is purely a perversion of taste, for none of the properties are present which make coffee so prized by the epicure.

Steeping, in which cold water is added to the coffee, and the mixture brought up to a boil, does not subject the coffee to so strenuous conditions. Local overheating and hydrolysis occur, but not to so great an extent as in boiling; and most of the effects of oxidation and volatization of caffeol are absent. However, extraction is rather incomplete, due to lack of thorough admixture of the water and coffee.

When coffee is to be made under the best conditions, the temperature of the water used and of the extract after it is made should not fluctuate. In the pumping percolator, as in the steeping method, the temperature varies greatly from the time the extraction is started to the completion of the operation. This is deleterious. Also, local overheating of the infusion occurs at the point of application of the heat; and because of the manner in which the water is brought into contact with the coffee, the degree of extraction shows inefficiency. Spraying of the water over the coffee never permits the grounds to be completely covered with water at any one time, and the opportunity offered for channeling is excessive. The principle of thorough extraction demands that, as the substance being extracted becomes progressively more exhausted, fresh solvent should be brought into contact with it. In the pumping percolator the solution pumped over the grounds becomes more concentrated as the grounds become exhausted; so that the time taken to reach the degree of extraction desired is longer, and an appreciable amount of relatively concentrated liquor is retained by the grounds.

Grinding Definitions
Powdered Like—flour.	Pulverized Like—not coarser than fine corn meal.
Very Fine and Fine Like—from corn meal to fine granulated sugar.	Medium Like—coarse granulated sugar.