THE PRESERVATION OF FOOD BY CHEMICALS 557 



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 

 preservative, but its presence in foods is readily detected, and it gives 

 rise to characteristic effects upon the consumer. Furthermore, such 

 foods are subject to special taxation as alcoholic products. Its use 

 as a food preservative is therefore limited. 



Wood smoke has been employed for centuries in the curing of meats. 

 Its antiseptic properties probably depend for the most part upon 

 creosote and pyroligneous acid, constituents of wood smoke which are 

 antiseptic and also undoubtedly poisonous in sufficient doses. Smok- 

 ing is a time-honored custom, however, and the amount of these 

 substances consumed with the smoked meat is doubtless exceedingly 

 minute. 



SUBSTANCES ADDED TO FOODS TO IMPROVE THE APPARENT QUALITY. 

 Several chemical substances are employed in various foods to im- 

 prove the appearance, or to simulate the taste of a higher-grade product. 

 In some cases the presence of these agents is known to the consumer, 

 and desired by him; in other instances they are employed to deceive 

 the purchaser. Butter coloring is quite generally used to produce the 

 color of June butter the year around; nitrates bring about a pleasing 

 red color in cooked pickled meats; copper sulphate is used to give a 

 more brilliant green color to prepared vegetable foods; sulphites restore 

 the red color of freshly cut meat to meat far from fresh; saccharine 

 devoid of food value gives a taste resembling sugar to a variety of 

 preparations at a great saving in cost to the manufacturer; carbonates 

 of the alkalies or alkaline earths, added to milk, neutralize the acids 

 resulting from bacterial decomposition and so keep the milk sweet; 

 inorganic acids added to weak vinegar increase its acidity. Some of 

 these practices are so universal and so well known that they are no 

 longer criticized; others, such as the use of chalk in milk, are generally 

 disapproved. 



