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.