2 BULLETIN 493, IT. S. DEPARTMENT OF AGRICULTURE. 
METHOD OF UNDERTAKING THE INVESTIGATION. 
It was felt that it would be wholly unsatisfactory to make this in- 
vestigation by means of laboratory brewings on a small scale, as the 
results thus obtained would not show the true conditions, because it 
is not possible in the laboratory to duplicate exactly the mashing or 
fermenting processes actually used in a commercial way. It was 
decided, therefore, to attempt, with the cooperation of several brew- 
eries, to make this study under the exact conditions prevailing in 
commercial plants. Access was secured to several breweries making 
different types of products from various kinds of raw materials, under 
such conditions that it was possible to obtain a complete history of 
the beer through its various stages to the finished product. One of 
the writers (Riley) watched the method of manufacture during its 
whole process and obtained samples of the product at the various 
stages of manufacture. Thus, it was possible to procure finished sam- 
ples with practically the same degree of certainty, as regards knowl- 
edge of composition and history, as would have been the case had they 
been prepared in the laboratory. 
In three different breweries manufacturing a wide range of products 
samples of the wort and beer were obtained in this manner, the entire 
process of manufacture being studied in detail. A record showing 
the kind and amount of raw materials placed in the mash and in the 
cooker was made of the samples collected from these three breweries. 
A record also was kept of the time and temperature of each operation 
until the mash was ready to run into the kettle. The filtering and 
sparging 1 of the mash, the time of boiling in the kettle, the amount 
of hops added and the point at which they were added, and the break 2 
of the wort were all noted. After the wort had been pumped from 
the kettle its course was followed through the hop jack 3 over the 
coolers to the settling tank. The specific gravity or Balling 4 of the 
original wort, the temperature at which the product was pitched, 5 
the aeration of the wort, the kind and amount of yeast added, as 
well as the time and maximum temperature of the primary fermen- 
tation, also were noted. The course of the beer through the storage 
vats, chip casks, and filters to the racks was watched, and samples 
of the wort and of the beer in its various stages of production were 
collected and examined. 
i Washing the grains with hot water to remove the extract or valuable constituents as completely as 
2 Precipitation and uniting, in the form of flakes, of the coagulable albuminoids, leaving the liquid clear. 
3 A filtering tank. 
* Percentage of solids in the liquor according to the Balling hydrometer. 
5 Pitching is the operation of adding the yeast to the wort. 
