12 
and to the different countries, due to unsettled world market. 
eonditions. 
2. Technical Features. 
Space does not permit us to go into any details of. the 
processes of manufacture and equipment. Nor is it within 
our purpose to deal fully with this phase of the subject. But 
the out!ines have to be noted in order to permit a general view 
into the industrial and economic features of these industries 
as well as to give a general idea of the nature of the products. 
Milk is a very complicated substance. It is not a mere 
mixture or solution in water of the various constituents mak- 
ing up the solids shown by the chemical analysis. The many 
attempts to make milk artificially have all failed. One of the 
simplest of its constituents, the milk fat, is itself a combina- 
tion of many fats and ethers. Still more complicated are the 
protein substances, so much so that no chemical formula can 
be given them, and it is still a matter of dispute among chem- 
ists whether there are one or two or twenty distinct »rotein 
bodies in the milk. Milk is in a sense a living substance, with 
chemical and physical as well as physiological properties in 
itself and as a food. The following table gives the average 
composition of normal cow’s milk and the margin of varia- 
tions in its principal constituents :+ 
Average % Variations 
(U.S. Dep. of Agric.) (Koenig) 
Water . . wesseeseaee 87.27 80.82—90.32 
Baths ejakisupesinc creas 3.68 ] 1.67— 6.47 
Casein « « sxisoesiw es 2.88 | 12.73 1.79— 4.23 
Albumen . ........... 0.51} Tot. Solids 0.25— 1.44 
Sugar (Laktase) ..... 4.94 | 2.11— 6.03 
SASH: a: zdeasddalaieauiceiieats 0.72 J 0.35— 1.21 
Fresh milk has very poor keeping qualities. It contains 
all the elements necessary for organic growth in such propor- 
tion and in such condition as to make it not only the most per- 
fect human food, but also a most favorable substratum for 
bacteria: growth. If not checked by cooling, and pasteuriza- 
tion or sterilization, fermentations quickly set in. The most 
important of these is that caused by lactic acid bacteria, which 
makes milk sour. Under the influence of the lactic acid, as 
also under the influence of rennet, an enzyme extracted from 
fWilliam A. Stocking: Manual of Milk Products. 
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