All About Coffee by William H. Ukers (best new books to read .TXT) π
CHAPTER II
HISTORY OF COFFEE PROPAGATION
A brief account of the cultivation of the coffee plant in the Old World, and of its introduction into the New--A romantic coffee adventure Page 5
CHAPTER III
EARLY HISTORY OF COFFEE DRINKING
Coffee in the Near East in the early centuries--Stories of its origin--Discovery by physicians and adoption by the Church--Its spread through Arabia, Persia, and Turkey--Persecutions and Intolerances--Early coffee manners and customs Page 11
CHAPTER IV
INTRODUCTION OF COFFEE INTO WESTERN EUROPE
When the three great temperance beverages, cocoa, tea, and coffee, came to Europe--Coffee first mentioned by Rauwolf in 1582--Early days of coffee in Italy--How Pope Clement VIII baptized it and made it a truly Christian beverage--The first Europe
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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 rΓ΄le 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.
Section of Roasted Bean Magnified 1,000 Times
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 itβthough neither a maximum of the non-volatile extractives nor a maximum of caffeol is obtainedβan 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.
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