DISINFECTANTS AND DISINFECTION. 183 



iionable chemical food preservatives which must be added to certain food sub- 

 stances in order to preserve them until they are to be consumed? Also the follow- 

 ing correlative rule should hold good: No chemical food preservatives 

 ■whatsoever should be used as such excepting in cases were: modern methods 

 of heat and cold sterilization and preservation fail or are inapplicable. 



The use of sugar and of salt in moderation are, of course, always permis- 

 sible, since these substances are essentials in many foods. The objection 

 and danger in the use of food preservatives lie in the fact that careless manu- 

 facturers are too prone to use them .in order to avoid employing harmless, 

 though perhaps less simple, and more expensive means of food preservation. 

 Chemical preservatives make it possible for the unscrupulous to use decom- 

 posed and otherwise objectionable food material. Furthermore, there is a 

 strong tendency to use chemical preservatives in excess, in spite of the 

 strictest legal quantitative limitations. 



The following is a brief summary of the more common food preservatives 

 and their use. 



The physical and mechanical means of food preservation have been 

 referred to, likewise the use of heat, cold, smoke, etc. One of the most 

 satisfactory methods of preserving foods, now employed in all up to date 

 canneries, is a combination of heat sterilization with air exclusion (air pump 

 and by displacement) . The food products as meat, corn, beans, asparagus, 

 peas, jams, jellies, preserves, etc., etc., are heated (100° C.) to destroy all 

 germ life, the containers (tins, glass) are also heated and then entirely filled 

 to exclude as much air (oxygen) as possible. Air (oxygen) is necessary for 

 the growth of bacteria, yeasts and moulds, hence a well filled container, with 

 a minimum of oxygen is less likely to show decomposition effects ("swells," 

 "leaks") than containers which are not well filled. It is claimed that whole- 

 some fruit, meat, etc., (free from decomposition), which is well sterilized by 

 steam heat and put up in well sterilized containers requires no chemical pre- 

 servative whatever. It is, however, customary, in the case of fruits, to add 

 sugar as a preservative and also for the purpose of rendering the article more 

 palatable. The sugar from sugar cane is quite universally used in prefer- 

 ence to the sugar from the sugar beet. This is no doubt due to the fact that 

 sugar beet sugar contains slightly more organic impurities and is, hence, under 

 similar methods of.use as to quantity, degree of heat sterilization, etc., slightly 

 more likely to undergo decomposition. 



Preservation of food substances by drying is coming into use more and 

 more. By this method it is possible to keep, for variable periods of time, a 

 great variety of foods as apples, peaches, pears, bananas, potatoes and many 

 other vegetables, besides bread, meats, eggs, mQk and other substances, 

 which were formerly more generally preserved by the canning method. 

 Eggs may also be preserved entire by giving them a coating of tallow, wax, 



