Dairying 387 



at about this temperature. Take samples of the cream and the skim- 

 milk and save them for testing. Mix the milk and cream that have 

 been separated, heat to 85 F., change the adjustment of the cream 

 screw, and run the milk through the machine again. Take samples as 

 before for testing. Change the adjustment of the cream screw, mix 

 the milk and cream, and separate again. Under favorable conditions 

 a separator should not leave more than ..1 per cent of cream in the 

 skim-milk and .05 per cent is what operators should try to secure. 



2. Testing for butter-fat. Test for butter-fat the samples of milk 

 and cream secured in the previous exercise. Follow carefully 'the 

 directions as given in the chapter. If there is not a Babcock testing 

 outfit among the school equipment, it will usually be possible to borrow 

 one from some one in the neighborhood. If this cannot be done, a 

 creamery or skimming station should be visited at a time when the 

 cream is being tested and the process observed closely. Small testing 

 outfits can be purchased cheaply from creamery supply houses, dealers 

 in agricultural laboratory supplies, and catalog houses. 



3. Impurities in milk. To test the quantity of impurities in milk, 

 secure several quarts from different sources, a roll of absorbent cotton, 

 a small piece of wire screen, several empty quart bottles, a dairy ther- 

 mometer, and a sauce pan. Place the wire screen over the mouth of 

 one of the empty quart milk bottles, spread a layer of absorbent cotton 

 over the screen, heat one of the quarts of milk to a temperature of 

 about 100 F. and pour it through the absorbent cotton into the bottle. 

 Remove the cotton and mark it to designate the source of milk that 

 was poured through it. Follow same instructions with other quarts of 

 milk. Examine the pieces of cotton. Unclean milk will leave a stain 

 on the cotton, and the dirtier the milk, the darker will be the stain. 

 Add varying quantities of dust to the different lots of milk, repeat 

 the experiment, and observe the results. Many creameries and cheese 

 factories make sediment tests of the milk of their patrons. If such tests 

 are made at local factories, ask to see the disks from different patrons. 



4. Cleanliness of dairy utensils. The equipment required for this 

 exercise is two pint jars with covers, a quart of fresh milk, a tooth pick, 

 and a dairy utensil that has unflushed seams. Fill the pint jars with 

 milk, scrape material from the seams of the utensil with the tooth pick, 

 and put this dirt in one of the jars, but not in the other. If no utensil 

 with unflushed seams is available, place some milk in a tin can or cup 

 that has unflushed seams, allow the milk to sour, pour it out, then 

 scrape the seams. Place the covers loosely over both jars and set them 

 away about five or six hours where the temperature is anywhere from 

 70 to 90 F. At the end of the time notice carefully the odor and 



