FREEZING AND COLD STORAGE 291 



frozen post-rigor^-^. Other investigations ^''•^^•^^■^^ report that fish frozen in 

 a pre-rigor condition are of high quaUty and that this method of freezing 

 is quite satisfactory. 



There is considerable controversy regarding effects of pre- and post- 

 rigor freezing on the quality of the frozen fish. When freezing fish at sea, 

 the practical considerations of fast and easy product handling offset any 

 theoretical advantage claimed for freezing in a post-rigor condition. In 

 the same vein, fish frozen ashore are customarily in post-rigor condition, 

 and no ill effects have been noted because of this. There are many factors 

 that have a greater influence on product quality than do pre- or post- 

 rigor freezing. 



Freezing. The relationship of freezing to quality changes is discussed 

 in comprehensive reviews by Dyer and Dingle ^2, Heen^^, Stansby^^, and 



Table 23.2. Effect of Chilled Storage 

 Age on Shelf Life of Frozen Whiting 



Reuter^^ Fast freezing results in large quantities of very small ice crys- 

 tals in the muscle, whereas slow freezing forms large crystals. However, 

 more recently theories have been advanced contradicting the early obser- 

 vations that the large ice crystals formed during slow freezing mechani- 

 cally damaged and ruptured the cells and were responsible for increased 

 drip in the thawed product. Lebeaux^^ found no evidence of cell puncture 

 during slow freezing. Love^^-^^-^S in investigations based on the premise 

 that cell rupture will liberate deoxyribonucleic acid (DNA) from the 

 nucleus of the cell, observed some correlation of DNA with cell damage 

 but did not conclusively demonstrate the effects of slow or quick freezing 

 on cell damage. 



Work conducted to date has been concerned primarily with the influ- 

 ence of the freezing rate on biochemical changes in the muscle tissue. Few 

 investigations have been conducted to determine if the freezing rate 

 afi"ects the quality of the product as judged by organoleptic examinations. 

 The author's experience indicates that there is no recognizable difference 

 between the organoleptic quality of products properly fast or slow frozen. 



