126 SAMPLING MILK AND CREAM 



composite samples that are tested at weekly, bi-weekly or 

 monthly intervals, and individual samples of part of the patronSj 

 that are tested daily. 



Single Milk Samples for Daily Tests. In this method the 

 milk of each patron's delivery is sampled and tested. This is 

 the most accurate and reliable method of sampling. The sample 

 is taken either into a glass jar from which later the correct 

 amount is transferred to the test bottle, or the sample may be 

 pipetted from the properly mixed milk in the weigh can direct 

 into the milk test bottle. In this way the extra work of handling 

 sample jars and of preparing the milk in the jar for the test is 

 made unnecessary, and all danger of fat separation before the 

 sample reaches the test bottle is avoided. This is obviously a 

 very accurate method of securing tests, but it involves a very 

 large, and under commercial conditions of operation an almost 

 prohibitive amount of work. On account of this objection this 

 method is not in general use and has been very largely 

 abandoned. 



Another practice of taking single samples is to take and test 

 samples from every other or every third delivery of milk. At 

 the end of the month or other period of payment, these individual 

 tests are averaged and the pounds of butter-fat are calculated 

 by multiplying the average test by the total pounds of milk re- 

 ceived for that period. This practice is obviously less reliable 

 than where single samples are taken and tested daily. However, 

 experimental results indicate that samples taken as often as every 

 third day give results which compare very closely with those 

 obtained from daily samples, as shown in the next table, illustrat- 

 ing relative accuracy of different methods of sampling milk, 



Composite Samples of Milk. The purpose of taking com- 

 posite samples is to reduce the labor and expense of testing. The 

 true composite sample consists of aliquot portions of milk of 

 several deliveries from the same patron. 



Jars for Composite Sampling. Composite sample jars must 

 have a tight seal in order to prevent evaporation of moisture. 



