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: