CANNING SARDINES 11 
EXPERIMENTS 
The drying apparatus used in the experiments is shown in Figure 
22. Its operation is described and the procedures followed in the 
experiments are given in the Appendix (pp. 191 and 192). 
MOISTURE REMOVED FROM RAW AND STEAMED TISH BY DIFFERENT DRYING 
CONDITIONS 
The factors influencing the drying rate of an object are the hu- 
midity and temperature of the air, its effective velocity, and the 
physical and chemical properties of the substance being dried. These 
factors, then, are the ones that must be studied with respect to the 
partial dehydration of raw and steamed fish. By varying one factor 
and making the others (including the fish, as nearly as possible) 
constant it is possible to get an idea of the effect of each. Many 
valuable data were obtained from experiments of this nature.*! 
These data show that increasing the temperature of the drying 
air brings about a marked increase in the amount of water removed 
from both raw and steamed fish, and this is also true to a lesser 
extent for increased air velocity. These results were expected. 
Increasing the amount of moisture in the drying air, however, gave 
somewhat unexpected results, in that this caused but little decrease 
in the rate of moisture removal, provided the humidity was not 
raised enough to cause some condensation to take place on the fish. 
It is evident from these experiments that moisture diffusion is so 
slow that even with high-humidity air the drying effect at the surface 
of the fish is sufficient to remove the water as rapidly as it comes to 
the surface. 
Considered from the standpoint of time, moisture removal, in 
partially drying the fish, is relatively rapid at first, after which it 
declines to a more nearly uniform rate. 
Under similar conditions steamed fish lose water more rapidly 
than raw ones. The flesh of steamed fish has been cooked, and this 
destroys its cellular structure, freeing water and making the fish 
much more porous. Therefore, moisture diffusion, being easier, 
takes place more rapidly. With steamed fish, too, greater advantage 
can be taken of the more rapid diffusion at higher temperatures. 
The danger of harming cooked fish by overheating is not so great 
as with raw ones. 
RELATION OF SIZE TO THE DRYING RATE 
Drying conditions being equal, small fish lose water more rapidly 
than large ones. Small fish offer, per unit of weight, a greater 
surface from which evaporation can take place than do larger ones. 
Further, diffusion in small fish takes place more readily because, 
being small, they heat quickly and the bulk of the moisture is nearer 
the surface in small fish than it is in larger ones. 

4 Table 35, p. 193, contains all the data. 
