120 PURE FOOD IN THE HOME 



Method: Soak half of the beans in water overnight. Crush them and 

 place a portion in each of three different test tubes. Add a few drops 

 of water to each test tube. Place one of these test tubes where it will 

 be kept warm, about 90 degrees. Place another in the refrigerator, 

 close the third with a wad of cotton and heat to the boiling point. 

 Crush one or two of the dried beans and put them in a test tube in a 

 warm place. Compare the odor in these tubes in three days. 



Conclusion: In which ones is decay taking place? Is this due to action 

 of bacteria ? Why do you think so ? Name at least two conditions 

 which favor bacterial growth and two conditions which are unfavorable 

 to it. 



The experiments show us that bacteria need moist 

 food and a warm temperature in order to grow well. Grains, 

 crackers, dried fish, and dried fruits all are examples of 

 foods which keep well because they contain very little water. 

 Boiling or sterilizing kills bacteria. It can be shown that 

 they need air, and that light is unfavorable for their rapid 

 growth. Sunlight is known to be one of the best germ 

 killers we have. For that reason sunlight is important in 

 both sleeping and living rooms. 



Foods most easily spoiled by bacteria. If you were 

 to select a large number of different foods and test them 

 to determine in which bacteria grow most rapidly, you 

 would find that the foods containing moisture; and a large 

 amount of protein, are most favorable for bacterial growth. 

 As the bacteria feed on this protein, it falls to pieces and 

 eventually rots. It is broken down by the action of bac- 

 teria into gases, liquids, and some solids. It has a char- 

 acteristic " rotten " odor, and poisons which come as a 

 result of the work of the bacteria. Some of the poisons 

 are called ptomaines. No food should be eaten that 

 smells badly or appears to be decayed. The use of com- 

 mon household preservatives in checking bacterial action 

 may be seen from this experiment. 



