134 U. § BUREAU OF FISHERIES 
with Maine herring and yielded similar results. The results to be 
obtained from high air velocities are too well known to require more 
than confirmation here.*° 
Inasmuch as drying is being accomplished at temperatures above 
the boiling point ‘of water, the amount of water vapor (steam) in 
the drying air will have little effect upon the rate of moisture loss 
from the fish. It has already been shown that increasing the 
humidity of the air has little effect upon the drying rate of fish that 
are being partially dehydrated, provided no condensation takes 
place on them. 
The following data from experiments 156b to 156e, Table 42, p. 208, 
illustrate the effect of time upon moisture removal from large, fat, 
oval-size pilchards by air having high temperature (300°) and veloc- 
ity (1,400 feet per minute): 10 minutes, 12.3 per cent loss in weight; 
15 minutes, 18.8 per cent; 20 minutes, 20.5 per cent; and 30 minutes, 
5.3 per cent. In these experiments the fish cooked 30 minutes, 
bel oad! and stuck to the flake excessively. Other experiments 
showed that 15 minutes is about as long a time as is advisable to 
subject large ‘‘ovals”’ to an air temperature of 300° to 352°. How- 
ever, more time can be used if the temperature be lowered. Air 
velocity has its effect, too, as high velocity tends to intensify tempera- 
ture effects. 
Small fish naturally dry more rapidly than larger ones. They heat 
through more rapidly and consequently are affected by the application 
of heat to a greater extent than are larger fish. It was necessary, 
therefore, to use lower air temperatures for quarter-oil fish in order to 
keep them from browning and sticking excessively. The subject of 
correct procedures for quarter-oil fish is discussed under the Maine 
experiments. 
Sticking of fish to flakes and to each other —In preparing the fish they 
had a tendency to be marred by the flake upon which they were cooked 
and to stick both to the flake and to each other. During cooking the 
fish softened and the weight of the fish pressed the skin firmly against 
the hot wires of the flake. Large fish, of course, were pressed more 
firmly than small ones, and they actually did mar to a greater extent. 
The gluey substances in the skins dried and caused them to stick to 
the flakes and to each other. Fat fish did not stick ‘as much as lean 
fish, and when the flake was oily this helped materially to prevent 
sticking, as did the use of clean flakes. The higher the air tempera- 
ture used the greater was the tendency of the fish to stick. 
When the flakes of fish were removed from the cooker, and also from 
the cooler, it was noticed that the fish usually had a tendency to stick 
to the flakes more than after they had stood for a short time. This 
behavior can be explained as follows: When the fish are removed from 
the current of air in the cooker their surface is dry. However, water 
continues to diffuse to the surface of the fish, where it is not removed 
as readily as it is when they are in the current of air, and this water 
softens the gluey substance that holds the skins to the flake. This 

50 See the discussion on moisture diffusion, p. 119, also Table 35, p. 193. If the results shown here are 
compared with moisture losses for similar velocities at lower temperatures, it will be noted that at the 
higher temperatures, where diffusion is relatively rapid, the effect of increased air velocity on moisture 
loss is more pronounced than at the lower temperatures. 
& See the discussion on p. 121. Experiments 137a and 138a, Table 42, p. 204, furnished additional evi- 
dence at a higher temperature. 
