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The Cornell Reading-Courses 



air-tight, the food will not spoil if held in a warm place. The spoiling of 

 food under such conditions must be owing to one of three things : 



1. Some flaw in the can, which makes it a so-called " slow-leaker." 



2. The presence of some micro organisms that have survived the cooking 

 process, in spite of all care. 



3. A drying-out of the rubber, and hence the breaking of the seal. 



In some factories where foods are canned in 

 glass jars, racks are made for holding the jars 

 upside down in an inclined position, keeping the 

 liquid constantly in the top of the can and 

 preventing the rapid drying of the rubber. 



To test canned jood. — Canned food should be set 

 aside for two or three days before storing, and 

 then should be tested as follows: Loosen the 

 clamp and grasp the can by the edges of the 

 glass top. If sterilization has not been com- 

 plete, if the can leaks, or if decomposition has 

 set in, the top will come off. If the top stays 

 on, tighten the clamp again and the food is 

 ready for storage. If the top comes off, reject that 

 can of food. 



To open the jar. — Run a knife blade under the 

 rubber and press firmly; if the top resists, pour a 

 stream of hot water over it. 



Fig. 86. — Manner of 

 testing 



Preservation cf Jood by means of preservatives 

 The word " preservative " is used to cover a wide range of substances, 

 that are used in food pniservation to prevent or retard the growth of 

 micro-organism.3. The us2 of preservatives is as old as the use of food. 

 Even primitive peoples were familiar with the preserving effects of salt 

 and smoke. With the growth of the food-preservation industry and the 

 development of new preservative substances has come the question, "Are 

 food preservatives harmful? " There has been a world-wide discussion 

 as to the legality of the use of certain of the preservatives since the claim 

 has been made that they endanger the health of the consumer. 



In regard to the action of preservatives it may be said, in a general way, 

 that any substance sufficiently active to destroy or check the growth of 

 micro-organisms should be at least tliorouglily questioned before it is 

 admitted to the ranks of our daily food supply. If a substance is active 

 enough to destroy life in micro-organisms, may it not have a similai 

 effect on the living tissue that lines the digestive tract? May it not be 

 detrimental when it reaches the blood system? Surely, only those pre- 



