Beard. — Canning of Sardines. 127 



Air drying is resorted to in Maine after the brined raw 

 fish have been steamed. These cooked fish still contain too 

 much water to can well so they are partially dried. Drying 

 of raw fish, however, prior to some form of pre-cooking pre- 

 sents a somewhat different problem from that of drying 

 steamed fish or fish to be canned raw. In these cases the 

 problem is more largely one of moisture, but to prepare fish 

 for pre-cooking the most important thing is to get them into 

 good physical condition for withstanding the rest of the 

 preparation for canning. It is a process of toughening the 

 skins and the removal of surface water and some internal 

 moisture so that the fish will undergo frying, steaming or 

 cooking in brine with minimum damage to themselves. The 

 actual amount of water removed is of secondary impor- 

 tance and may vary some without detriment to the final pack, 

 especially if plans are laid to remove more or less water in 

 the subsequent preparation. 



If one looks into the nature of air drying it will be found 

 that when air is heated it has a greater moisture absorbing 

 capacity at the higher temperature. It is therefore possible 

 to take air which is already saturated with moisture, (as on 

 a rainy day) , heat it, and use it for drying fish. The mov- 

 ing, warm air striking the fish warms them, furnishing the 

 heat needed to vaporize the water and then carries the water 

 vapor away from the fish. With other conditions equal and 

 favorable, an increase in the temperature of the air, or in its 

 velocity, or a decrease in its moisture content, will bring 

 about an increase in the amount of moisture removed from 

 an object being dried. The application of these principles 

 is limited, however, by the physical and chemical proper- 

 ties of the object being dried, and practical considerations 

 which present themselves. 



The experimental work upon the behavior of the raw fish 

 under different drying conditions has shown that the amount 

 of moisture in the drying air has but little effect upon the 

 rate of moisture removal from the fish, providing no conden- 

 sation of water on the fish takes place. Increasing the 

 temperature, however, brings about a marked increase in 

 the amount of water removed and this is also true for in- 

 creased velocity. With other conditions equal, either an 

 increase in temperature or in velocity will bring about 

 greater heat transfer from the air to the fish, thus increasing 

 the vaporization of the water, and its diffusion from the in- 

 terior to the surface. In this way a greater loss of water 

 from the fish is brought about. High temperatures acting 

 upon large *'pound-oval" size fish for any considerable 

 length of time softens them considerably and causes some oil 



