CONDENSED AND DESICCATED MILKS 649 



and must be kept cool to prevent decomposition. "Evaporated 

 milk" is concentrated milk filled in cans and sterilized after the 

 cans are sealed. 



Sweetened condensed milk should contain at least 28 per cent, 

 of milk soUds and 8 per cent, of fat. Condensed evaporated 

 skimmed milk should have at least 20 per cent, of milk solids. 



Gail Borden introduced condensed milk on a commercial scale 

 in 1856. Since that time the industry has developed to such an 

 extent that in 1909 — according to Wells, who gives a detailed 

 account of the industry — there were more than 300 milk condens- 

 ing plants in the United States, representing an investment of 

 $15,000,000. The value of the total output in 1909 was $33,563,129. 

 Recently the use and export of concentrated milk has increased 

 enormously. It takes the place of fresh milk in soldiers' camps, 

 since fresh milk is difficult to obtain, and is growing in favor with 

 the housewife, who, although she may have access to fresh milk, 

 likes to keep it along with other staple goods. 



Condensed or evaporated milk may be made from skimmed 

 milk or from whole milk. Skimmed milk is condensed to one- 

 fourth its volume and whole milk to one-third. The product sold 

 in bulk is usually made from skimmed milk, while canned milk is 

 made from whole milk. Only clean milk should be used for con- 

 densing, as abnormal flavors become more concentrated during the 

 condensing process. The acidity of the milk must be low, as other- 

 wise the condensed product will coagulate. Manufacturers are 

 very careful in the selection of the raw milk they intend for con- 

 densing purposes, and employ experts to detect off-flavors. 



Milk is condensed principally by two methods: either by the 

 use of a vacuum pan in which the milk is evaporated under reduced 

 pressure so that the boiling-point lies at 130° to 135° F. ; or by the 

 use of hot air. In the second case the milk is heated to 140° F. 

 and hot air then blown into it. The hot air takes up the water 

 from the milk, and by this means the desired consistency is ob- 

 tained. Before condensing, the milk is passed through a cream 

 separator, and if whole condensed milk is to be prepared the cream 

 is mixed with the condensed skimmed milk. 



After canning there is some change in the physical condition 

 similar to that in milk when it stands quietly. The fat rises, while 

 the heavier constituents sink. To prevent the rising of the fat 

 the milk is sometimes homogenized before condensing takes place. 



Evaporated (unsweetened milk) is normally free from bacteria, 

 since it is sterilized after canning. Sweet condensed milk is not 

 sterilized, and usually contains bacteria, although they rarely 

 multiply in view of the high concentration and sugar content of the 

 product. However, some investigators have found large numbers 



