CHAPTER III.* 

 THE PRESERVATION OF FOOD BY COLD. 



INTRODUCTION. 



In recent times cold storage has become of very great importance 

 in the preservation of perishable food stuffs, and foods preserved by cold 

 usually command a higher market price than those preserved by other 

 methods. This is probably due primarily to the fact that the general 

 appearance of refrigerated food resembles that of the perfectly fresh 

 article, in many instances very closely. Moreover, in many instances 

 cold storage, for a reasonable length of time, preserves not only the 

 appearance and the nutritive value, but also the chemical composition, 

 and even the delicate flavors of the original articles, so important in deter- 

 mining market value. - The great economic importance of this industry 

 is at once apparent, for it aims to preserve unchanged the over-abundance 

 of one locality for transportation to another, and the over-production of 

 one season of the year for subsequent use. 



THE EFFECTS OF REFRIGERATION UPON FOOD STUFFS IN GENERAL. 



The decomposition of foods depends upon the activity of their own 

 intrinsic enzymes to some extent, but more especially upon the activity 

 of foreign microorganisms bacteria, yeasts and molds. Cold acts as a 

 preservative, not by destroying these microbes, but by retarding or in- 

 hibiting their activity. In general, cold not only retards the growth of 

 the microorganisms but delays their death also, tending to preserve 

 them as well as the food stuff unchanged. 



In discussing the refrigeration of foods we may consider three periods 

 of treatment, (i) the removal of the heat or chilling of the food, (2) the 

 prolonged storage at low temperature, (3) the subsequent warming of 

 the food before sale or consumption. 



CHANGES DURING CHILLING. The period of cooling is a relatively 



* Prepared by W. J. MacNeal. 



395 



