Butter Moisture-Tests. 523 



Preparing the sample for testing 



This is one of the most important and difficult operations in the 

 process of testing butter for moisture. Water and fat do not readily 

 mix, and there is a constant tendency for the water to ooze out of the 

 butter. When the water separates from the butter it is difficult to dis- 

 tribute it again evenly through the sample. After repeated trials of 

 several months we found the following method of preparation to give 

 the most uniform results: 



Place the sample to be tested in a glass container which has a fairly 

 wide mouth, so that the sample can be stirred. A quart fruit jar is 

 useful for this purpose. Then hold the container in warm water until 

 the butter begins to melt. Remove the container from the warm bath 

 and thoroughly mix the melted with the unmelted butter. In the 

 laboratory a long-bladed cheese knife was found very useful for mixing 

 the butter. A wooden stirrer should not be used as it is likely to take 

 up moisture from the sample. The process of melting the butter and 

 mixing it with the unmelted butter is repeated until the sample contains 

 no lumps and the entire mass is about the consistency of thick cream. 

 The container is then transferred to cold water and the sample thor- 

 oughly mixed as the butter cools. There is a tendency for the fat around 

 the outside of the container to harden rapidly and force the water 

 toward the center of the jar. For this reason special care must be 

 taken to keep the butter scraped off the sides of the container and 

 thoroughly mixed with the softer butter in the center of the jar. When 

 the sample is all of about the texture of ordinary butter the mixing 

 may be stopped. If the process has been properly done the water 

 will be evenly distributed throughout the sample and any desired 

 amount of the latter may be removed for testing. 



The above process is a modification of the one recommended by 

 the Association of Official Agricultural Chemists. The Official method 

 directs to shake the sample instead of stirring it when cooling. In 

 our tests we have obtained better results by stirring. In melting the 

 butter, do not. use too hot water, as there is danger of driving off some 

 of the moisture. The jar containing the sample should be kept covered 

 to prevent the evaporation of moisture. 



THE CHEMICAL GRAVIMETRIC METHOD 



This is the most accurate method for testing butter for moisture, 

 and is the one employed by chemists. It is performed by drying a 

 weighed sample (about two grams) in a jacketed copper water-oven 



