yO A DAIRY LABORATORY GUIDE 



EXERCISE XIV 



BABCOCK TEST, MICROSCOPIC APPEAR- 

 ANCE OF MILK, USE OF RENNET 



1. Test the sample preserved at the last exercise. 



2. Examine under the high-power i.iicroscope cream, 



whole milk and skimmed milk. Make a draw- 

 ing of each field. Describe fully the difiference 

 in the appearance of the fat globules in each 

 of the three fields. 



3. Heat 18 grams of skimmed milk to about 100° 



F. and add four drops of rennet; shake thor- 

 oughly and let stand. Note the length of time 

 it takes the milk to curdle. 



4. To one-half a teacup of water add six drops of 



sulphuric acid. Add three drops of this solu- 

 tion to 18 grams of milk. Heat to about 100° 

 F. and note the time it takes for milk to coagu- 

 late. Compare length of time with that re- 

 quired in No. 3. 



5. To about 20 grams of skimmed milk add six drops 



of sulphuric acid and shake thoroughly. Note 

 time it takes the milk to coagulate and com- 

 pare the coagulum with that obtained when 

 rennet is used. 



6. Measure out two 25 cc. samples of skimmed milk. 



Warm to 80' F. To one sample add five drops 

 of rennet; to the other add five drops of sul- 

 phuric acid. Note and compare the length of 

 time it takes each to coagulate. What two 

 things hasten the action of rennet in milk? 



