130 U. S. BUREAU OF FISHERIES 
from removing blood by brining and distribution of salt throughout 
the fish by this method, that process of preparation that comes 
nearest to removing only water from the fish is best. 
In addition to considerations as to quality of the product, there 
arises, of course, the important question of production costs. These, 
if possible, should be lowered. 
Frying in oil, as now practiced, adds objectionable oil from the 
fry bath to the final product, unless the oil in the fry bath is changed 
frequently, and the cost of doing this as often as is advisable is 
prohibitive. Frying also removes considerable oil, salt, and soluble 
extractives from the fish. The loss of these valuable substances is 
especially high when fish are steamed. Fish are also likely to break 
up more or less during the steaming operation. In Maine it is 
generally conceded that steaming detracts from the quality of the 
fish. 
Research has shown how improvements can be made in these two 
processes. It has not shown, however, how the difficulties men- 
tioned can be eliminated. Other processes do not have these dif- 
ficulties, but they do not offer sufficient other advantages over 
present practices to enable them to supplant those now used in 
Maine and California. 
In the first paragraph of this section an outline was given of what 
should constitute an ideal process for preparing the fish. As far as 
quality goes, the raw-packing process comes nearest to meeting 
these demands, both from a theoretical standpoint and from the 
results of experiments when applied to the preparation of fish for 
the pound oval pack. The process falls down otherwise; it takes too 
long to remove the necessary water from the fish. Drying research 
indicated that this time can not be shortened materially. Other 
information gained from this study, with that from the other inves- 
tigations, did point the way to a new process for preparing the fish, 
which not only lacks the disadvantages of frying in oil and steaming 
but possesses a number of commercially important advantages over 
the old methods. This new process is discussed first from a theo- 
retical standpoint. 
HIGH-TEMPERATURE, HIGH-VELOCITY AIR AS A MEANS OF PREPARING 
THE FISH 
Air-drying is accomplished in the following manner: Moving 
warm air striking the fish furnishes the heat needed to vaporize the 
water and then carries this water vapor away. After surface water 
is vaporized more can be removed only after it has diffused from 
within to the surface. It will thus be seen that the rate of moisture 
loss depends upon how rapidly this diffusion takes place. The 
higher the temperature of the fish the more rapid is the diffusion. 
The obvious thing to do, then, to bring about rapid drying, is to heat 
the fish as quickly as possible to as high a temperature as is practi- 
‘able and to keep this temperature until the desired amount of 
water has diffused from the fish and been removed by the current of 
air. The rapidity of heating depends on the rate of heat transfer 


46 This process is covered by the following patents: United States No. 1553296, Sept. 8, 1925; Spain, No. 
5335, May 27, 1925; France, No. 597059, Nov. 12, 1925; Portugal, No. 14135, Nov. 26, 1925; Canada, No 
260084, Apr. 27, 1926; and Great Britain. No. 241169, Nov. 30, 1926. Norwegian patent allowed (appli- 
cation No. 32745, Apr. 7, 1925) but no patent number yet available. 
