CHEMICAL COMPOSITION 165 



sugar in condensed milk crystallizes very readily and causes the 

 condensed milk to become sandy and settled. Chemical ana- 

 lyses of this sugar sediment show that it consists principally 

 of milk sugar. The primary cause of this property lies in the 

 fact that sweetened condensed milk contains so little water 

 (about 26.5 per cent.) that the milk sugar is present in the form 

 of a supersaturated solution ; therefore, any condition which 

 favors sugar crystallization will tend to produce this defect. 1 

 Milk sugar requires from five to six times its weight of water 

 at ordinary temperatures for complete solution. In sweetened 

 condensed milk the milk sugar has access to only about twice 

 its weight of water (12.5 to 15 per cent lactose to 25 to 27 per 

 cent, water). 



Ash. The per cent, of ash is largely dependent on the 

 degree of condensation. It usually varies from 1.5 to 2 per cent. 

 It is quite constant in fresh milk (normal fresh milk contains 

 uniformly about .7 per cent. ash). The per cent, of ash in 

 sweetened condensed milk may serve, therefore, as a reason- 

 ably reliable factor in determining the degree of condensation. 

 The heating of milk, before condensing, precipitates and renders 

 insoluble a portion of the mineral solids, principally the lime 

 salts. 



Sucrose. The purpose of the presence of sucrose in this 

 product is to preserve it. Most of the sweetened condensed 

 milk on the market contains from 37 to 43 per cent, sucrose, or 

 cane sugar. Wider variations, however, are not infrequent. In 

 some cases analyses showed as low as 30 per cent, and in others 

 as high as 48 per cent, cane sugar. Cane sugar dissolves in one 

 half its weight of water, so that under normal conditions there 

 is sufficient water in the condensed milk to keep the sucrose 

 in solution. The amount of sucrose in milk does not appreciably 

 affect the power of the milk to dissolve milk sugar, nor does 

 the per cent of lactose present materially affect the power of the 

 milk to dissolve sucrose. 



Specific Gravity. The specific gravity of sweetened con- 

 densed milk falls within the limits of 1.24 to 1.35. Foreign 



1 For further details on causes of settled sweetened condensed milk see 

 Chapter XXIII, page 196. 



