All About Coffee Part 140

I.D. Richheimer[380], attacking the cotton cloth filter, said:

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 pa.s.sage 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-cla.s.s 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 quant.i.ty 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 pa.s.sage 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 coa.r.s.e 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 coa.r.s.er the grind the faster the flow, which permits a larger quant.i.ty 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 r.e.t.a.r.d 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 quant.i.ty of coffee, as to allow an unr.e.t.a.r.ded 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 pa.s.s 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 gla.s.s 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, gla.s.s-filter, percolator, and boiling pot followed in the order named.

At the 1917 convention of the National Coffee Roasters a.s.sociation, 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 coa.r.s.er 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 Ma.s.sachusetts Inst.i.tute 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 Inst.i.tute began to "test the results of the committee's work by purely a.n.a.lytical methods."

The first report on the research work at the Ma.s.sachusetts Inst.i.tute 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 quant.i.ties 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 a.s.sociation, 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 gla.s.s (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 a.n.a.lyzed 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 coa.r.s.er 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 quant.i.ty 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 gla.s.sware, 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 a.s.sure 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 appet.i.te 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.

CONSt.i.tUENT CONCEPTS. The roasting of green coffee causes an alteration in the const.i.tution of its const.i.tuents, 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 quant.i.ty 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 const.i.tuents which are water-soluble after the torrefaction may be generally cla.s.sified 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 quant.i.ty that their only role 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.

[Ill.u.s.tration: SECTION OF ROASTED BEAN MAGNIFIED 1,000 TIMES]

We know that very small quant.i.ties 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 const.i.tuents 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.