NUTRITIVE VALUE OF J'ISH AND SHELLFISH 



511 



Table 6. — Effect of freezing and storage on the composition of food fishes 

 [Analyses of the edible portion on the moist basis] 



During storage the fish v/ere kept glazed; that is, dipped into water 

 immediately after freezing and thus covered with a thin coating of 

 ice. The object of this glaze is to prevent mechanical damage to 

 the skin of the fish and at the same time prevent evaporation or loss 

 of water. If fish were not glazed, their skins would rapidly dry out 

 and take on a most unattractive appearance. It may seem strange 

 that moisture will evaporate from frozen fish at a temperature of 

 only 5° above zero; but this has to be guarded against constantly in 

 the storage of frozen products. The same thing happens to a cake 

 of ice standing in the open air. Even when the temperatures are 

 far below freezing it will soon be noticed that the ed^es of the cake 

 become rounded, and that it gradually shrinks in size and finally 

 disappears. The water in the form of ice has evaporated directly 

 from the solid state into the state of vapor without any apparent 

 sign of becoming a liquid. This is exactly what happens to frozen 

 fish when stored without glazing. 



While the storage period which these experimental fish passed 

 through was probably about three times as long as that commonly used 

 in commercial practice, it is evident that there was no detectable change 

 in chemical composition or food value during that period. The glaze 

 on the fish apparently prevented the evaporation of any considerable 

 amount of water, and, as could be expected, there was no change in 

 the fat, protein, or ash content, except such variations as are always 

 found when individual fish are being analyzed. In addition to the 

 work reported in the table given above, Clark and Almy (1920) 

 found no significant changes in the more refined analyses which they 

 made on the individual nitrogenous substances found in fresh fish. 

 These substances are supposed to be quickly influenced by any signs 

 of decomposition, but such changes were not detected. In conclusion, 

 we may say that the process of freezing and storing of fish in cold 

 rooms IS one in which there is no appreciable change in the quality 

 or food value of the fish. 



