Condensed Milk and Milk Powder 



153 



in excess of the amount which normal fresh milk contains, is con- 

 ducive of the formation of lumps. 



Excessive amounts of acid in condensed milk may be the result 

 of fermentations, usually due to a poor quality of sugar, or of the 

 use of acid flux in the making and sealing of the tin cans. Con- 

 densed milk that shows acid or gaseous fermentation usually 

 contains lumps. The acid which it develops as the result of the 

 fermentation, curdles the casein with which it comes in contact. 



One of the most common channels through which condensed 

 milk may become contaminated with acid mechanically, is the use 



Fig. 49. Machine for rinsing and sterilizing the tin cans 



Courtesy of The Sprague Canning Machinery Co. 



of cans, in the manufacture of which acid flux was used. The acid 

 flux generally used contains zinc chloride.- The flux precedes the 

 solder and some of it is bound to sweat through the seams into the 

 interior of the cans. Zinc chloride is a highly poisonous product 

 and its use in the manufacture of tin cans, which are intended for 

 receptacles of human food, should be prohibited by law. Aside from 

 its injurious effect on the health and life of the consumer, its pres- 

 ence, even in small quantities in condensed milk, is a detriment to 

 its market value. In such cans there accumulate, usually along the 

 seams, lumps and smeary substances which have been found to 

 consist of casinate of zinc. 



Most commercial soldering fluxes consist largely of zinc 

 chloride and are highly acid, although many of these are advertised 

 as acid-free fluxes. In order to avoid condensed milk containing 



