108 THE FISHING INDUSTRY 



They can be preserved 



(1) By boiling, and packing immediately afterwards 

 in air-free containers. 



This process is, of course, the basis of the great meat 

 packing industry. The meat is packed in a tin, the tin 

 and its contents are heated in steam or boiling water 

 until the meat is cooked and all the decay organisms are 

 destroyed. The tin is then sealed, air-free and air-tight. 



(2) By freezing. 



Cold storage is a widely used method of preserving 

 foodstuffs. The low temperature prevents the growth 

 and development of decay organisms and, as long as 

 the foodstuff is kept sufficiently cold, arrests decay. 



Prehistoric animals long extinct are sometimes 

 found firmly embedded in the Polar ice, as fresh as they 

 were on the day they were drowned. 



It is found that the stability and subsequent quality 

 of frozen meat or fish depend directly upon the manner 

 in which it has been frozen. It may be frozen in air, 

 or when immersed in brine. Of these two methods the 

 latter is much quicker, because brine is over twenty-five 

 times as good a conductor of heat as air is. During the 

 slower air-freezing process the quality of the flesh is im- 

 paired by the separation of the contained water into com- 

 paratively large crystals of ice. This leads to the displace- 

 ment of the membrane and tissues of the meat, so that 

 in thawing again the meat drips and becomes tough. 

 When immersed in brine freezing occurs too rapidly for 

 this separation of water to occur to any marked extent. 



The keeping qualities of brine-frozen fish also are 

 greater than those of air-frozen fish, owing to the pro- 

 tecting coating of ice which effectively prevents contact 

 with bacteria or mould spores. 



(3) By drying. 



Primitive man preserved his meat by drying it in the 



