THE PRESERVATION OF FOOD BY CHEMICALS. 407 



INORGANIC FOOD PRESERVATIVES. Boric acid and borax are weak 

 antiseptics, practically a saturated solution of boric acid being necessary 

 to inhibit ordinary bacterial growth. When employed as a dry powder 

 on the surface of meats, boric acid prevents the growth of mold, and most 

 of it is removed from the food before consumption. When incorporated 

 with butter it is eaten, and 0.5 to i.o g. may be taken daily in this 

 way alone. The effect of such amounts of boric acid upon the consumer 

 is still a disputed question. Wiley,* after a recent extensive investigation, 

 concluded that small doses of either boric acid or borax continuously 

 administered for a long period create disturbances of health. 



Nitric acid and nitrous acid and their salts are food preservatives of 

 some theoretical interest because it is well known that some bacteria 

 readily decompose fairly strong solutions of nitrates, and also oxidize or 

 reduce nitrites. Apparently, however, this is true only in neutral or 

 alkaline solutions, and in the presence of free acid the activity of these 

 microbes is quickly inhibited. The preservative effect of nitrates and 

 nitrites is best ascribed to the liberation of minute quantities of free nitric 

 and nitrous acids from these salts, and these substances are without value 

 as preservatives in foods which are alkaline in reaction. The effects of 

 the ingestion of nitrate or foods preserved with nitrate upon the consumer 

 has been investigated by Wiley, who concluded that the deleterious effects 

 are slight and less clearly detected than in the case of the other preserva- 

 tives. Minute but variable amounts of nitrites occur in foods preserved 

 with nitrates, but whether these amounts are sufficient to produce the 

 specific nitrite effect upon the blood circulation of the consumer has not 

 yet been definitely ascertained. 



Sulphurous acid and the sulphites are rather extensively used in 

 chopped meat (Hamburg steak) and in cider and wines. The addition 

 of sulphite to chopped meat serves a three-fold purpose, retarding bac- 

 terial decomposition, producing a red color on the exposed surface, and 

 removing odors of decomposition. It thus not only delays decomposition, 

 but also to a certain extent conceals the decomposition which has already 

 occurred. The ingestion of moderate quantities of sulphites in food 

 has at times been followed by acute gastric derangement in man, and 

 prolonged feeding of meat containing sulphites has been followed by 

 inflammatory changes in the kidneys of experimental animals. 



Fluorides have been used to a slight extent in beverages, but acute 



*U. S. Dept. Agr., Bureau of Chemistry, Bull. No. 84, Part I. 



