428 SCIENCE PROGRESS 



unfrozen condition this cannot be relied upon to last longer 

 than thirty days without the risk of substantial deterioration, 

 so that importation of chilled beef from places from which the 

 transit takes longer than three weeks is not usually undertaken. 

 If frozen beef of quality equal to the best chilled beef could 

 be obtained the importation of beef from any part of the 

 earth could be brought about as successfully as, for instance, 

 that of frozen mutton. 



Other important advantages of freezing are economy of 

 space and convenience in handling. Frozen meat can be 

 much more closely packed than chilled meat and requires 

 much less attention, and the financial advantages accruing from 

 these facts far more than compensate for any extra cost result- 

 ing from keeping the produce at a lower temperature. 



Certain animal produce has been found suitable for pre- 

 servation in the frozen condition, among which may be men- 

 tioned mutton, rabbits, and some species of fish. In other 

 cases where, for the reason already mentioned, it would be 

 extremely advantageous to preserve the material in the frozen 

 condition, freezing can be used, but produces, as a rule, a 

 decided deterioration. 



By applying scientific principles and scientific methods 

 of research there is, however, every reason to believe that 

 methods of freezing can be devised which will prevent deteri- 

 oration in these food substances. In other cases, as with fruit, 

 freezing has so far proved impossible. 



As has already been indicated, the principle involved in 

 storing meat and other commodities in the frozen state is the 

 replacement of the liquid water by solid ice, and in this way 

 removing the liquid medium in which chemical reactions take 

 place and micro-organisms flourish. Thus W. D. Richardson 

 says : " It is the solid state and not any specific temperature 

 (e.g. o° C.) which is the limiting condition for growth and 

 reproduction of micro-organisms." 1 We have already referred 

 at the end of the second part of this series of articles to the 

 principal difficulty encountered in the preservation of organic 

 tissue by freezing. This is, that after thawing, water which 

 was previously bound in the cell contents becomes free and 

 drips from the tissue so that a loss of fluid occurs, and this 

 " drip," as it is sometimes called, may carry with it appreci- 

 able quantities of nutritive material. This difficulty is especi- 

 ally noticeable in the case of frozen vegetable tissue. If, for 

 instance, a potato, carrot, or an apple be frozen and subsequent- 

 ly thawed, on squeezing the tissue in the hand, water will run 



1 W. D. Richardson, "The Cold Storage of Beef and Poultry," Premier 

 Congres International du Froid, Rapports et Communications, vol. 2, pp. 261-316, 

 Paris, 1908. 



