290 



PRESERVATION METHODS 



Quality changes in the fresh state take place much more rapidly than do 

 those in the frozen condition and are quite different in nature. The former 

 result chiefly from autolysis and growth of bacteria^ '^•^ and the latter 

 from dehydration and oxidation^- ^^-^^ Frozen fish prepared from partly 

 spoiled fish have a much shorter frozen shelf life than fish freshly frozen. 

 Reay^^ found that the shelf life, or quality, of frozen haddock used for 

 smoking decreased considerably because of an increase in the storage 

 period of the unfrozen raw material. His results are not applicable to 

 frozen fillets since the very nature of freezing alone may seriously impair 

 the suitability of a product for smoking. ^lore recently, Peters^^ found 



Table 23.1. Relative Suitability of Fishery Products for 

 Freezing and Frozen Storage 



that the chilled storage age of whiting seriously affects the quality of the 

 frozen packaged product. The results of these investigations are shown 

 in Table 23.2. 



Much work has been done on assessing quality changes in chilled fish 

 and in frozen fish, but little information is available on the relationship 

 of prefreezing quality to the quality of the frozen product. 



Another consideration in freezing fish may be whether or not the raw 

 material has passed through rigor mortis. Banks, et al.,^'^-'*' found that 

 eviscerated cod stored in ice for up to three days after catching could be 

 frozen satisfactorily with little loss of cpiality. It has also been suggested 

 that fish frozen in a pre-rigor condition are of lower quality than fish 



