THE PRESERVATION OF FOOD BY CHEMICALS 555 



lose this property. None of the ordinary food preservatives approaches 

 this ideal very closely. 



INORGANIC FOOD PRESERVATIVES. Boric acid and borax are weak 

 antiseptics, practically a saturated solution of boric acid being neces- 

 sary 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 an extensive 

 investigation, concluded that small doses of either boric acid or borax 

 continuously administered for long periods 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 effect 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 preservatives. Small quantities of saltpeter 

 appreciably delay the digestive action of a mixture of pepsin and 

 hydrochloric acid (artificial gastric juice) upon coagulated egg white in 

 a test tube, f 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 



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

 f MacXeal and Kerr: Unpublished work. 



