Sweetened Condensed Milk — Cooling 95 



and time, and the quality of the product was poor. It was soon 

 found that the imperfect hand stirring caused excessive sugar 

 crystaUization, which made the milk sandy. The sudden chilling 

 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. 



Later the hand stirring was completely superseded by 

 mechanical stirring, paddles closely scraping the sides of the cans 

 being 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 motion 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 cross-bars and the power started. The 

 cans should be heavily constructed to stand rough usage, with- 

 out suffering indentations. Cans with irregular, depressed, or 

 bulged sides cause the paddles to do poor work. ■ Such cans 

 should be slipped over a wooden horn, or other contrivanc-e., and 

 the indentations hammered out with a mallet. The paddles a^e 

 held stationary by cross-bars and are forced against the peripl^y 

 of the cans by springs. Attention should also be paid toiSie 

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

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

 to scrape the sides of the cans properly. m 



The sweetened condensed milk should be cooled gradually. 

 Sudden chilling should be avoided. This is best accomplished 

 by warming 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 to twenty minutes before any cold water is turned 

 into the tank. After that, cold water is turned in slowly until 

 the temperature of the. milk has fallen to about 70 degrees F. The 



