72 Condensed Milk and Milk Powder 



to cool naturally, i. e., if no effort were made to cool it promptly, 

 it would become thick and cheesy in texture in a short time. It is, 

 therefore, essential that it be cooled at once. Formerly, this was 

 done by setting the cans in tanks containing ice water and stirring 

 the milk with a stick. This was a very crude method, it involved 

 much hard work and time, and the quality of the product was poor. 

 It was soon found .that the imperfect hand stirring caused excessive 

 sugar crystallization, which made the milk sandy. The sudden chil- 

 ling and irregular stirring of a saturated sugar solution like sweet- 

 ened condensed milk are favorable to the formation of sugar crystals. 

 Where the stirring is imperfect and irregular, all the milk is not 

 kept in sufficient motion to insure uniform and gradual cooling. 

 The milk next to the side of the cans is chilled too abruptly, 

 favoring the formation of crystals. Vigorous stirring in itself is 

 conducive of sugar crystallization. 



The hand stirring has been completely superseded by mechan- 

 ical stirring. Paddles closely scraping the sides of the cans are now, 

 used. Instead of setting the paddles in motion, they are stationary 

 and the cans revolve. The principle is similar to that of the vertical 

 ice cream freezer. Heavy iron tanks, with a capacity of twelve to 

 forty-eight 40-quart cans, are used for this purpose. The bottoms 

 of these tanks are equipped with a system of cog wheels, set in mo- 

 tion by means of a gear at one end of the tank. The wheels have a 

 diameter large enough to carry one can each. The cans are set on 

 these wheels, the paddles are inserted and fastened to cro^s-bars 

 and the power started. The cans should be heavily constructed to 

 stand rough usage, without suffering indentations. Cans with ir- 

 regular, depressed, or bulged sides cause the paddles to do poor 

 work. Such cans should be slipped over a wooden horn, or other 

 contrivance, and the indentations hammered out with a mallet. The 

 paddles are held stationary 'by cross-ibars and are forced against the 

 periphery of the cans by springs. Attention should also be paid to 

 the pivots on which the cog wheels rest. If they are warped, the 

 wheels do not run true, so that it is not possible for the paddles to 

 scrape the sides of the cans properly. 



The sweetened condensed milk should be cooled gradually. Sud- 

 den chilling should be avoided. This is best accomplished by warm- 

 ing the water in the cooling tank to about 90 degrees F., before the 

 cans are set in. The cans are then allowed to revolve for fifteen 



