PLAIN CONDENSED BULK MILK 131 



Striking. The striking-, or sampling and testing for gravity 

 is done with a Beaume hydrometer, the same, or a similar one, 

 as is used for evaporated milk. The scale should extend to 15 

 degrees Beaume. The batch should be struck before and after 

 superheating. 



Factories which standardize their product to a certain 

 established density, usually condense the milk to a point slightly 

 beyond that desired. Then, after superheating, they determine 

 the amount of water required to reduce the finished product, and 

 then add the required amount of water before the condensed milk 

 is cooled. It is advisable to use distilled water for this purpose. 



Ratio of Concentration. The ratio of concentration varies 

 largely with the fat content of the milk, although the locality 

 and season of year are also influencing factors. Whole milk is 

 condensed at the ratio of about three parts of milk to one part of 

 condensed milk, while the ratio of concentration for skim milk 

 is about 4 to 1. The proper density varies somewhat with locality 

 and season of year. Roughly speaking, whole milk has reached 

 the proper density when the Beaume reading at 120 degrees F. 

 is about 10 degrees B. and skim milk has reached about the 

 proper density when the Beaume reading at 120 degrees F. is 

 about 14 degrees B. When the ratio of concentration exceeds 

 4 to 1, there is danger of gritty condensed milk due to the pre- 

 cipitation, in this concentrated product, of crystals of milk sugar. 



Cooling. The plain condensed bulk milk is usually drawn 

 into 40 quart milk cans, placed in cooling tanks containing re- 

 volving cogwheels, as described in Chapter VI, under "Cooling 

 Sweetened Condensed Milk," and is cooled to as near the freezing 

 point as facilities permit. 



Recently this crude and laborious method of cooling has 

 been superseded in many of the larger condenseries by more 

 modern ways. While the plain condensed bulk milk becomes 

 too thick and sluggish during the process of cooling to make 

 possible the use of surface coolers, and internal-tube coolers, it 

 can be readily cooled in vats equipped with revolving discs, or 

 in horizontal coil vats especially constructed for this purpose 

 and in which the lower part of the vat is constricted and the coil 

 sets very low in this constricted part, so as to agitate the milk 

 vigorously and at the same time prevent the incorporation of air, 



