CHAPTER IV* 

 THE PRESERVATION OF FOOD BY CHEMICALS 



The addition of preservative substances to foods is a very ancient 

 practice, and as no extensive equipment is required it is one of the 

 cheapest ways of preserving food, especially on a small scale. The 

 resulting alteration of the food in appearance and composition is greater 

 than when it is preserved by cold storage, for the preservative substance 

 added becomes a more or less permanent constituent of the food, but 

 the changes are not necessarily undesirable. The addition of chemical 

 preservatives is often practised in conjunction with desiccation or cold, 

 or sometimes even in canned or bottled foods sterilized by heat. All 

 the substances employed as preservatives owe whatever efficiency they 

 may possess to their ability to restrict the activity of microorganisms, 

 that is, their antiseptic properties. 



THE EFFECTS OF PRESERVATIVES UPON FOODS IN GENERAL 



In only a few instances are chemical preservatives added to foods to 

 be sold as fresh foods, and these practices are generally regarded with 

 disfavor. Their most important use is in the prepared foods, the pre- 

 servative being incorporated with the food during the process of 

 preparation for storage. 



THE PROCESS OF CURING. The procedures employed necessarily 

 vary with different foods. Physical alterations in the food, such as 

 changes in form, texture and water content are usually involved, as 

 well as the solution of the preservative in the juices of the food. 

 Chemical changes due to the intrinsic enzymes of the food, to the 

 various accessory procedures such as drying, cooking or soaking in 

 pickling solution may produce marked alteration. In some cases the 

 preservative reacts chemically with some constituent of the food. 

 During the curing process microbic activity may be more or less 

 prominent at various times, playing its part in the chemical changes. 



* Prepared by W. J. MacNeal. 



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