90 



OUR FOOD SUPPLY 



Refrigeration. Bacteria do not grow and multiply at 

 low temperatures. For this reason refrigerators have 

 come into general use as a method of preventing the 

 spoiling of food. Refrigeration should not be confused 

 with sterilization, however, as a cold temperature 

 does not kill bacteria it simply prevents their 

 growth. If water or food is impure, freezing will not 

 purify it. The temperature within a refrigerator 

 should never be above 50 F. to keep foods from spoil- 

 ing. 



In Unit II, Topic 1, problem 4, pages 31-32, you 

 learned how cold was produced by evaporation in the 

 electric refrigerator and cold-storage plant. Review 

 that problem at this time and be sure that you under- 

 stand the construction and operation of these modern 

 refrigerating devices. 



In the ice refrigerator the low temperature is pro- 

 duced by melting ice. The box is well insulated to 

 keep outside heat from entering. Thus any heat that 

 is secured to melt the ice must come from the ma- 

 terials inside the box. This chills them and prevents 

 the growth of bacteria. 



Since cold air is heavier than warm air, convection 

 currents are set up inside the box which keep the air 



\Ruth Cunliff Russell 



FIG. 131, REFRIGERATED MARKET 



cir 

 ch 

 bo 



ulating continually. The air near the ice becomes 

 led, starts to fall toward the lower portion of the 

 :, and pushes the warm air toward the top. 



Exercise. Is the temperature the same in all parts of 

 a r 'frigcratorf Devise a method of testing this problem 

 ana, after investigating, record the results in your note- 

 book. Suggest where meat and milk, both of which must 

 be kept very cold, should be placed in a refrigerator 

 to : ecure the lowest temperatures. 



Ip recent years another substance known as "dry 



ice" has come into common use for refrigerating ice 

 cream and other foods. Dry ice is solid carbon diox- 

 ide. It is made by compressing the gas carbon dioxide 

 and then letting it expand. The expansion removes 

 sufficient heat to solidify the gas. Since dry ice is 

 about 140 degrees Fahrenheit colder than ordinary 

 ice, a much smaller quantity is needed for cooling. 



What is food adulteration? In 1906 the Congress 

 of the United States passed what is commonly known 

 as the Pure Food and Drug Act. The purpose of this 

 law was to protect the consumer of prepared foods 

 from fraudulent practices in their preparation, and 

 preservation. Foods may be adulterated in any of the 

 following ways : 



Substances may be added to cheapen the food. 



Substances may be mixed with a foodstuff to reduce 

 or change its quality. 



Valuable parts may be removed from a foodstuff. 



Coloring matter may be added to conceal damaged 

 or inferior materials. 



Poisonous materials may be added for purposes of 

 preservation. 



Vegetable or animal substances may be used which 

 are regarded as unfit to eat. 



Exercise. Study the labels on canned foods and see how 

 many you are able to collect that would illustrate any 

 of these ways of adulterating foods. Suggest foods that 

 may 'be adulterated in other ways. Paste in your note- 

 book any labels you may find and write out the sugges- 

 tions of foods that may be adulterated in the other ways 

 mentioned above. 



The Pure Food and Drug Act prohibits the use of 

 certain substances in prepared foods and requires 

 that, when certain others are used, this fact be clearly 

 printed on the container. In this respect the law has 

 been beneficial. Since 1906, however, many new sub- 

 stances have come into use, some of which are more 

 harmful than those specified by the law. 



This act provides only for those foods that are sold 

 from one state to another. Adulteration of foods man- 

 ufactured and sold locally is possible unless state and 

 city laws prevent and unless authorities in these 

 places are exceedingly alert. Thus it is quite evident 

 that our pure food laws are somewhat out of date and 

 in need of some revision that will better protect from 

 injurious adulterants those persons who depend on 

 prepared foods. 



Of course, not all adulterants are harmful. Corn 

 sirup is frequently used as an adulterant in maple 

 sirup or honey. Oleomargerine is sold as a substitute 

 for butter. Neither of these substances is harmful ; 

 they are, in fact, wholesome foods. Because these sub- 

 stances are cheaper than the foods for which they are 

 substituted, they are regarded as adulterants accord- 

 ing to the Pure Food and Drug Act of 1906. 



