346 THE FOODS WE EAT 



We cook foods because the (1) _ temperature kills the germs 

 and because the cooking softens tough fibers, thus making food 

 taste better and (2) _ more easily. Heating substances for a 

 period long enough to kill germs is called (3) __ Cold will 

 (4) _ the growth of bacteria, but it does not always (5) _ 

 them. Milk, even when handled under the most sanitary condi- 

 tions, spoils very easily. One way to help prevent its spoiling 

 too soon is a process called (6) __ In this process the milk 

 is heated to (7) _ F., for a period of (8) _ minutes. Heating 

 the milk to too high a temperature destroys (9) _ (10) _ and 

 makes the milk less useful. Cold as well as heat is used to prevent 

 food decay. (11) _ of air is important in (12) _ because it 

 helps to keep the constant low temperature. Electric (13) _ and 

 the use of (14) _ (15) _ , are two modern methods of refrigera- 

 tion. Thermos bottles use a (16) _ to keep the temperature con- 

 stant. Water may be cooled in iceless refrigerators by the action of 

 (17) __ Since bacteria cause foods to spoil, the kitchen should be 

 kept spotlessly (18) __ It should be well (19) _ to prevent the 

 (20) _ of germs by flies. 



STORY TEST 



PAUL WAS ABSENT JUST ONE DAY FROM CLASS 

 Read carefully and critically. List all the errors and suggest corrections. 



Of the many things that cause milk to spoil bacteria are the 

 worst, but they can be checked by cooling and killed by freezing. 

 One common cause of milk souring is the thunderstorm and there is 

 no help for it. If you wish to prevent mold from forming on food, 

 you can do any one of three things. Keep it cool, keep it hot, or 

 keep it very moist. Since microorganisms are plants, they die if 

 kept away from the sunlight very long. In canning fruits and 

 vegetables, it is necessary to heat them to 144 F. in a process 

 called Pasteurization. They must then be quickly put into cans 

 and sealed so that they are air-tight. Foods so preserved will 

 keep indefinitely. The principle of the electric refrigerator is that 

 the refrigerator has electric insulation in all the walls. An ordinary 

 refrigerator keeps just the heat out, but the electric refrigerator 

 keeps both electric and heat energy out. 



THE REVIEW SUMMARY 



In preparing a summary of what you have learned in this unit, 

 you will want to place emphasis on the big ideas which have come 



