FREEZING AND COLD STORAGE 289 



ated with dry ice. Subsequently, many technological and engineering 

 improvements were made in the transportation and marketing of frozen 

 seafood, thereby making it possible to market these products on a large 

 scale. 



The frozen sea fish industry has grown considerably since Piper's first 

 freezing of fish a century ago, and now over 350 million pounds of frozen 

 fishery products are produced annually in the United States. 



Maintenance of Product Quality 



The quality of frozen fishery products is influenced by many different 

 considerations. Among the most important are composition of fish, pre- 

 freezing handling and treatment, method of freezing employed, and the 

 environment to which the frozen product is subjected during storage and 

 handling. Of principal concern here is the temperature and humidity of 

 the cold-storage area and the protective packaging or glazing afforded 

 the product. It is difficult to pinpoint precisely how much each of the 

 above factors individually influences the quality of frozen seafood. 



Fish not readily amenable to freezing have a low resistance to adverse 

 conditions of treatment; thus, they must be handled under almost ideal 

 conditions. In contrast with this are those products which lend themselves 

 to freezing and have a certain built-in resistance to malpractices. Like- 

 wise, a product of excellent quality prior to freezing will take more 

 punishment than one of only marginal quality when frozen. 



Composition of Fish. The composition of fish has a significant effect on 

 whether or not a product can be successfully frozen. Fish with high oil 

 content are, in general, more susceptible to oxidative color and flavor 

 changes than are those that contain only small quantities of oil. However, 

 oil content is not the only factor involved here. According to Stansby^-^ 

 pink salmon, containing only 6 per cent oil, develops rancid odors and 

 flavors much quicker than does king salmon containing as much as 16 

 per cent oil. 



The relative suitability of different fishery products for freezing and 

 frozen storage is indicated in Table 23.1. Today, 100 years after the in- 

 ception of freezing, little is known of the biochemical properties of fishery 

 products and how they influence the suitability of the product for freezing. 

 For example, the North American lobster cannot be frozen satisfactorily 

 because of serious textural changes; yet the spiny lobster, or craw fish, 

 is readily amenable to freezing. Atlantic Coast oysters, blue crabs, and 

 clams are not generally suitable as frozen foods, but little information is 

 known as to why this is so. 



Prefreezing Treatment. The condition of the raw material to be frozen 

 significantly influences the subsequent quality of the frozen product. 



