408 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



gastric derangement and depression of the heart are caused by rather 

 small quantities, and probably on this account the salts of hydrofluoric 

 acid have not come into very general use as food preservatives. 



ORGANIC FOOD PRESERVATIVES. Formic acid (H'COOH) and 

 acetic acid (CH 3 'COOH) are produced by microbic activity and their 

 preservative action appears to depend more upon the degree of acidity 

 than upon the character of the acid radical. Both these acids appear to 

 be utilized as food in the body of the consumer. 



Benzoic acid and benzoates are rather extensively employed in pre- 

 pared vegetable food products, such as jams and catsups. The antiseptic 

 effect seems to be due wholly to free benzoic acid, even where it is added 

 in the form of the salt, but the action is not due merely to the acidity 

 (i. e. the hydrogen ion). Benzoic acid is not utilized as a food in the 

 body, but is excreted by the kidneys in the form of hippuric acid. It has 

 been said to produce irritant effects upon the stomach and the kidneys, 

 and to arrest the action of digestive enzymes in dilute solutions, but the 

 Referee Board* of the United States Department of Agriculture, after 

 extensive investigations, concluded that small doses of sodium benzoate 

 mixed with food are not injurious to health, and do not impair the quality 

 or nutritive value of the food. 



Salicylic acid and the salicylates have been used for much the same 

 purposes as benzoic acid, and there does not appear to be much dif- 

 ference between the two acids, either in their efficiency as preservatives 

 or in their possible deleterious effects upon the consumer. Salicylic acid 

 is more expensive. After extensive investigation Wiley f has concluded 

 that the addition of salicylic acid and salicylates to foods is reprehen- 

 sible in every respect, this conclusion corresponding to the results of 

 similar work by the same investigator J upon benzoic acid. 



Formaldehyde is very efficient as an antiseptic, delaying microbial 

 decomposition when added to foods in very small quantity. Its use for 

 this purpose is generally condemned, partly because of its hardening or 

 ''fixing" effect upon the protein constituents of the food, tending to make 

 them more indigestible. Its use in milk and milk products, though still 

 practised to some extent, has been prohibited by law in some states. 



Alcohol (CH 3 .CH 2 OH), in sufficient concentration, is an excellent 



* U. S. Dept. Agr. Report No. 88, May, 1909. 



t U. S. Dept. Agr., Bureau of Chemistry, Bull. No. 84, Part II, 1906. 



J U. S. Dept. Agr., Bureau of Chemistry, Bull. No. 84, Part IV, 1908. 



