FOOD MATERIALS AND HOW TO DETECT THEM 



21 



Conclusion. State briefly in not more than four sentences 

 what are the tests for protein. 



Suggestion. Repeat these tests, using meat, cereals, 

 flour, cheese, milk, bread, potatoes, and other articles, and 

 determine which give the best tests for protein. 



Note. Millon's reagent is made by mixing one part mercury 

 by weight with two parts nitric acid (concentrated commercial). 

 When the mercury is all dissolved, dilute with twice the volume of 

 water. 



Biuret reagent is made as follows : to 1000 cc. of a 10 per cent 

 solution of caustic soda in water, add drop by drop 10 cc. of a 3 per 

 cent solution of copper sulphate, stirring constantly while the solu- 

 tions are combining. The same test is obtained if the substance is 

 first treated with strong caustic soda and then very dilute copper 

 sulphate. 



Another Protein Test 



To a substance to be tested, add a drop of saturated cane 

 sugar solution in water. Then add a drop of pure sulphuric 

 acid. If proteins are present, the substance will assume a 

 deep red color. 



8. STARCH 



Object. To learn how to detect 

 the presence of starch. 



Apparatus. Laundry starch, flour, 

 potatoes, solution of iodine, test tubes, 

 lamp, etc. 



Method. Place a little starch in 

 a test tube with water. Shake it 

 vigorously. Does it dissolve? Does 

 it froth as the egg did? Filter and 

 allow the filtrate to evaporate. Is 

 there any starch residue? 



