406 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



every respect as valuable from the standpoint of nutrition as the corre- 

 sponding fresh foods. The difference is not dependent upon a change in 

 the food-principle content, but must be sought rather in slightly altered 

 composition of the food and the specific effects of newly formed substances, 

 and especially in the possible effects of the continued ingestion of the con- 

 tained chemical preservatives upon the consumer. 



THE EFFECTS OF FOOD PRESERVATIVES. 



The essential characters of a food preservative include antiseptic 

 action to prevent decomposition of the food, and absence of evident 

 poisonous or deleterious influence upon the consumer. It follows there- 

 fore that the effects of food preservatives upon the consumer, if they exist 

 at all, are at any rate not easily recognized, and on account of the economic 

 importance of the questions here involved this field of scientific research 

 has been energetically cultivated by investigators with different viewpoints, 

 and the results of investigation have been discussed with some heat. The 

 modern pure-food laws have required more specific knowledge upon these 

 points for their proper administration, and have stimulated extensive 

 investigations, but it is still too early to regard the facts as finally and 

 definitely ascertained. 



SUBSTANCES WHICH PRESERVE by THEIR PHYSICAL ACTION. The 

 preservative effects of sodium chloride seem to depend entirely upon the 

 high osmotic tension of strong salt solutions, and the same may be said of 

 cane sugar. When diluted so as to be eaten with relish, these substances 

 are themselves properly classed as foods, without deleterious effects upon 

 ordinary individuals. 



SUBSTANCES WHICH PRESERVE BY THEIR CHEMICAL ACTION. These 

 preservatives inhibit the activity of microorganisms in a different way, 

 not by withdrawing water from the microbic cell, but by entering into 

 chemical combination with the living substance in such a way as to hinder 

 its activity, or by entering into chemical reactions with the food to produce 

 new substances capable of attacking the microbic protoplasm in this way. 

 The ideal chemical food preservative would be one which, without altering 

 the food substance, would exhibit this poisonous property toward living 

 protoplasm until the food was ready for consumption, and then would 

 suddenly and permanently lose this property. None of the ordinary food 

 preservatives approaches this ideal very closely. 



