52 



DAIRY LABORATORY GUIDE 



EXERCISE 3 



VARYING THE AMOUNT OF ACID IN TESTING 



Object : To determine the effect upon the reading of the 

 test from using varying amounts of acid. 



Apparatus : Samples of whole milk, four milk test bottles, 

 small graduate, and testing outfit. 



Steps: 1. Arrange the bottles and number them from 

 1 to 4, respectively. 



2. Prepare the samples of whole milk for testing accord- 

 ing to the previous exercises. 



3. Add 10 c. c. of acid to bottle No. 1. 



4. Add 17.5 c. c. of acid to bottle No. 2. 



5. Add 25 c. c. of acid to bottle No. 3. 



6. Add the regular amount of acid to bottle No. 4. 



7. Mix all the tests well; then complete the test as usual. 



Fig. 9. The relative proportion of butter-fat and serum in dairy products. 



These diagrams will serve to show the relative proportion 

 of butter-fat and serum in dairy products. The proportion 

 of serum decreases as the butter-fat increases; therefore less 

 acid is required when testing products rich in butter-fat. 

 Figure No. 1 represents skimmilk, buttermilk, and whey; No. 

 2, whole milk; and No. 3, average cream. 



