HOW MAY WE KEEP FOODS FROM SPOILING? 339 









PROBLEM V. HOW MAY WE KEEP FOODS FROM 

 SPOILING? 



How May We Keep Foods from Spoiling? We have 

 seen from what has just been said that bacteria live and 

 grow under certain favorable conditions. Our next 

 question will be to find out what unfavorable conditions 

 will prevent the growth of these organisms. 



What Cooking Does to Foods. If we examine a bit of 

 raw potato under the microscope, we find that the starch 

 contained in it is in 

 little cells surrounded 

 by thick walls. If we 

 examine a bit of well- 

 cooked potato under 

 the same microscope, 

 we find the cell walls 

 have largely disap- 

 peared. Cooking 

 softens and breaks 

 down these tough walls and makes vegetables and meat 

 less tough and more palatable, thus aiding digestion. 

 More than this, cooking makes foods safe, as it destroys 

 germs and other living organisms which might grow if 

 taken into the body. Cooking, with the addition of salts 

 and condiments, improves the flavor of foods. 



Home Experiment. What Temperature Is Unfavorable for the 

 Growth of Microorganisms ? Take a small number of beans, soak 

 them, and put an equal number in three cups containing small 

 amounts of water. Place one cup in the ice box near the ice; 

 another in a moderately warm place ; and the third in the oven or 

 some place where it is exposed to rather high heat. Be sure to keep 

 the amount of water in each cup about the same. Examine the 

 cups from day to day. In which one of the three cups do you find 

 the most decay? Observe the growth of mold in bread and the 

 growth of yeast in a molasses solution in cold, moderate, and very 

 warm temperatures. What results do you obtain? 



Conclusion. What conditions are unfavorable for growth? 



The effect of cooking on the cells of potato. 



Notice the walls of the cells and the enclosed 



starch grains in the uncooked potato. What 



has happened in the right-hand figure ? 



