176 BACTERIA, YEASTS, AND MOLDS 



eral rules should always be followed where food is put aside 

 for preservation at a low temperature. 



1. Cool the food as quickly as possible. This should be 

 done before covering and setting aside for keeping. 



2. Use every possible device for avoiding moisture. 



3. Use food quickly after taking it from its place of stor- 

 ing, for such food when warmed decays rapidly. 



The Use of Heat 



The easy destruction of bacteria by heat suggests a 

 means for increasing the keeping properties of many foods. 

 Liquid foods may first be boiled and then cooled as quickly 

 as possible, after which they may be put away in cold 

 places for preservation. It is necessary that the material 

 should actually be boiled, since insufficient heat is not 

 only useless but frequently detrimental. If a putrescible 

 material is simply steeped in warm water and then put 

 away, it will spoil rapidly; if it is boiled it may be pre- 

 served for some time. Boiling is useful for such materials 

 as soups, stews, or any Hquid not injured by boiling. It 

 must be remembered, however, that boiling will not pre- 

 serve the material indefinitely; it simply delays the 

 spoiling. It kills the bacteria present, but others can get 

 in later. 



