THE ALUMNI JOURNAL, 



189 



milk is reduced to within two degrees of 

 the cooling medium, after which it is 

 standardized to a definite percentage of 

 milk fat. All possible germs are thus at 

 once arrested in their development, a 

 marked contrast to the vacuum process, 

 where the milk is held warmed and 

 ready for the vacuum pan for one or two 

 hours, but unfortunately under very 

 favorable conditions for germ growth. 

 The cold milk from the cooler flows into 

 shallow metal pans properly mounted on 

 trucks and track, connecting with the 

 freezing closets, in which are arranged 

 direct ammonia gas expansion pipes. 

 The pans have an upper surface area of 

 about fifty square feet, and one or two 

 hundred gallons have been found a 

 proper charge for each pan. The rapid- 

 ity of the freezing effect can be doubled 

 by spreading the milk over one hundred 

 square feeet of surface. The temperature 

 of the freezing closet is kept at or near 

 zero, and the milk is permitted to freeze 

 until a film of ice is formed, when an 

 automatic stirring apparatus breaks the 

 ice into particles or crystals. This oper- 

 ation of film freezing and breaking up 

 continues until all of the milk is con- 

 verted into a mushy mass of ice crystals, 

 with thick milk held between the crys- 

 tals of ice. This mixture of crystals 

 and thick milk is poured into a rapid- 

 running centrifugal machine, with an 

 instant separation of the condensed milk 

 from the crystals, the latter forming a 

 heavy bulk of hard snow. When as- 

 sayed this snow shows about two-tenths 

 of one per cent, of milk solids. 



The first freeze usually separates one- 

 half of the water in the milk, and two 

 additional freezes are required to reduce 

 it to proper consistence. 



Estimating that milk contains eighty- 

 six per cent, of water, seventy-eight 

 per cent, of this water can be frozen to ice 

 and readily separated with a centrifugal 



speed of fifteen hundred revolutions per 

 minute in a thirty-inch basket. 



The limit of condensation is not a 

 question of converting water into ice, 

 but rather a problem of detaching the 

 heavy, tenacious condensed milk from 

 the ice crystals, which is accomplished 

 by increasing the speed of the cen- 

 trifugal proportionate to the density of 

 the milk. 



In practice the condensation is usually 

 four to one on a milk fat basis, which 

 forms milk of sufficient density to meet 

 the public demand. When the con- 

 densed milk is diluted with water, it 

 dissolves completely, forming milk of 

 normal flavor, taste, and from which 

 cream will separate as irom ordinary 

 milk. When subjected to the Babcock 

 method of fat testing, the fat separates 

 clear as with ordinary milk, quite unlike 

 this test when applied to the condensed 

 milk by the boiling process, which gives 

 a mixture of clear and broken-down 

 products, that prevent a satisfactory 

 reading of the milk fat. 



In keeping qualities the cold process 

 condensed milk will rank with the so- 

 called pasturized standard, the destruc- 

 tion of germ life at 32 F. seems quite as 

 extensive, as the heating or pasturizing 

 by heat at 174 F. 



The prolonged keeping qualities of ice 

 cream at low temperature, often for weeks 

 without impairment of taste or flavor, 

 naturally confirms the statement that no 

 detrimental changes are wrought in the 

 milk by the freezing temperatures, and 

 careful chemical examination fails to 

 discover decomposition effects in the 

 constituent parts of the milk. 



Butter and cheese can be made from 

 the diluted condensed milk and the action 

 of the organized ferments is the same as 

 in normal milk. 



The cold process has been applied to 

 other products requiring condensation, 



