164 PRACTICAL DAIRY BACTERIOLOGY 



milk is useful for some things, it can never be substituted for 

 milk in an ordinary diet. It has undoubtedly a place in our food 

 products, but it does not, and it cannot, take the place of milk 

 for most purposes. 



Unsweetened condensed milk is also upon the market. This 

 material is sterilized by heat after being condensed to the desired 

 volume. It is then sealed and it keeps simply because it is steril- 

 ized. It has the advantages and disadvantages of sterilized 

 milk, and while an article of value for some purposes it adds 

 little to the solution of the milk problem of cities. 1 



The preservation of sweetened condensed milk is due to its 

 great sugar content, which prevents the growth of bacteria. But 

 sugar will not prevent the growth of yeasts. We have already 

 seen (page 9) that yeasts can grow in sugar solutions. While 

 bacteria do not usually spoil condensed milk it is sometimes 

 found, to the misfortune of the manufacturer, that yeasts may 

 ferment it. Immense losses have occurred in the condensed 

 milk industry in the last few years by the growth of fermenting 

 yeasts. Bacteria can usually be found in condensed milk also, 

 but they do not develop. Hence, if yeasts do not produce 

 trouble, the material keeps well for a long time. 



Evaporated Cream. This is a milk product which has been 

 on the market for a few years, although not very widely used. 

 It consists of milk with a varying amount of cream, evaporated 

 to less than half its bulk and thoroughly sterilized by heat. It 

 is then sealed in cans and will keep indefinitely. It has some 

 of the disadvantages of sterilized milk, having much the same 

 taste. Little is known of its digestibility, although laboratory 

 tests 2 have shown that it is equally digestible with raw milk. 

 Like condensed milk it has its place among food products, but 

 it will not replace raw milk as an article of food. 



1 Kasdorf. Rev. Gen. d'Lait, I., p. 73, 1901. 

 2 Mojonnier. Med. News, 1905. 



