THE HYGIENE OF THE DINING ROOM 



59 



kinds of nutrients are proteins, fats, carbohydrates, water, 

 and mineral matters. All of our foods contain one or more 

 of these nutrients. In selecting foods we are concerned 

 chiefly with the first three nutrients. Examples of pro- 

 tein are white of eggs, the lean part of meats, and the gluten 

 of flour; examples of carbohydrates are sugar and starch, 

 such as is. found in vegetable foods; examples of fats are 

 butter and the fatty portions of meats. 



LABORATORY EXERCISE 9 



Purpose. To test foods for different kinds of nutrients. 



Materials. Various kinds of foods, iodin, nitric acid, 

 ammonia. 



Directions, i. To test for starch. Heat a little corn starch 

 in water and allow it to cool. Then add a few drops of a dilute 

 solution of iodin in alcohol. A blue color shows the presence 

 of starch. In a similar way test a number of common foods. 



2. To test for proteins. Add a little nitric acid to a piece 

 of meat in a test tube and boil. Pour out the acid, rinse the 

 meat in water, and add ammonia. The yellow color is a test 

 for proteins. Test a number of foods for proteins. 



3. To test for fats. Place a piece of butter on a sheet of 

 writing paper and warm over a flame till it melts. Then rub 

 off the butter and notice the change that has taken place in 

 the paper. This effect in making the paper transparent is a 

 test for fat. Test other foods for fat. 



4. Put records in the form of the following table. 



Put the names of the foods in the first column and put a 

 check opposite each food in the proper column to correspond 

 with the tests. 



