150 Testing Milk and Its Products. 



This can easily be done by means of special sampling 

 devices (see 179 et. seq. ). As the quantities of the milk 

 delivered from day to day by each patron vary but little 

 perhaps not exceeding 10 per cent, of the milk delivered, 

 the error introduced by taking a uniform sample, e. g., 

 an ounce of milk, each time is, however, too small to be 

 worth considering in factory work, and the method of 

 composite sampling described is generally adopted in 

 separator creameries and cheese factories, where the 

 payment of the milk is based on its quality. 



178. By this method of composite sampling each lot of 

 rich, medium or thin milk receives due credit for the 

 amount of butter fat which it contains, and errors that 

 might arise from testing only one day's milk at irreg- 

 ular intervals are avoided. In order to obtain reliable 

 results by composite sampling it is essential that each 

 lot of milk sampled shall be sweet and in good condition, 

 containing no lumps of curdled milk or butter granules. 

 The m'ilk is of course always evenly mixed before the 

 sample is taken. 



179. b. Drip sample. Composite samples are sometimes 

 taken at creameries and cheese factories by collecting in 

 a small dish the milk that drips through a fine hole or 

 tube placed in the conductor spout through which the 

 milk runs from the weighing can to the receiving vat or 

 tank. A small portion of the drip collected each day is 

 placed in the composite sample jar, or the quantity of 

 drip is regulated so that all of it may be taken. In the 

 latter case the quantity of milk delivered will enter into 

 the composite sampling as well as its quality, and the 

 sample from, say 200 Ibs. of milk will be twice as large 

 as the sample frem 100 Ibs. of milk. 



