CANNING SARDINES 117 
raw or steamed fish by subjecting them to the action of moving warm 
air has been found to be an essential step in all commercial methods 
of preparing the fish. The principles underlying this step and their 
practical application are, in general, unknown to sardine canners. 
Then, too, the behavior of raw rand steamed fish under various drying 
conditions has not yet been worked out. Accurate knowledge of 
this latter point is necessary to permit application of the fundamental 
principles of air drying to the designing of apparatus and to the 
improving and cheapening of this necessary step in the preparation 
of the fish.” 
THE ROLE OF DRYING IN THE PREPARATION OF THE FISH 
In Maine, in order to obtain a satisfactory product, it 1s necessary 
partially to dry the fish after they have been steamed. Partial dry- 
ing prior to some form of cooking presents a somewhat different 
problem from the drying of ste eamed fish or fish to be canned raw. 
In the latter cases the problem is essentially one of moisture removal. 
In the former case the most important thing is to get the fish into 
good physical condition for withstanding the rest of the preparation 
forcanning. It is a process of toughening the skins and of removing 
surface water and some internal combined moisture, so that the fish 
will withstand frying, steaming, or cooking in brine with minimum 
damage. The actual amount of water removed is of secondary 
importance and may vary somewhat without detriment to the final 
pack, especially if plans are laid to remove more or less water in the 
subsequent preparation. In the frying process, for example, a study 
of different cannery procedure shows considerable variation in the 
amount of water removed by drying, yet the final product of each 
plant is satisfactory. The large amount of water removed by frying 
and draining overnight tends to equalize smail differences in loss of 
moisture due to drying. In this study of partial dehydration it is 
important to keep these ideas in mind. 
GENERAL PRINCIPLES OF DEHYDRATION 
A good understanding of the fundamental principles of air drying, 
on the part of the sardine canners, will be of much assistance in im- 
proving drying conditions in the industry. For this reason part of 
what is known about air drying and its application to drying fish is 
explained here. 
Air is acombination of gases that, when dry, can take up or associate 
with itself a definite quantity of water vapor for each temperature 
at which it may be. The quantity of water vapor that can be taken 
up by a given weight of dry air increases very rapidly with rising 
temperature. For ‘instance, 1 pound of dry air at a temperature of 
122° can take up 7.4 times as much water as an equal amount of air 
at 62°, and at 182° the amount is 62 times that at 62°. This example 
indicates why it is possible on a rainy day, when the temperature is, 
say, 62° and the air is already saturated with moisture, to heat the 
air by passing it through a steam coil and then to have it take up 
moisture from wet fish. Contrary to popular opinion, heat does 
not dry air; it only makes it possible for it to associate more mois- 

= 42 zee various kinds of drying apparatus used by the California sardine canners are described on pp. 
