CHAPTER XI 
MILK AND MILK PRODUCTS 
Mix is the special secretion of the mammary glands and is generally 
used for food by man. Fresh milk is amphoteric to litmus with a spe- 
cific gravity heavier than water—1.030. It has a yellowish color and a 
characteristic odor. On account of its chemical composition, which is 
mentioned later, it is susceptible to many undesirable changes. Many 
of these are brought about by microorganisms and, therefore, may be 
controlled by holding the milk in an environment, the factors of which 
are detrimental to bacterial development, 
CHEMICAL CONSTITUENTS OF MILK 
The constituents of milk have been classified by Van Slyke and 
Bosworth (1914) in the following manner: 
1. Milk constituents in 2. Milk constituents part- 3. Milk constituents en- 
true solution in ly in solution and tirely in suspen- 
milk serum. partly in suspen- sion or colloidal 
sion or colloidal solution. 
solution. 
a. Sugar a. Albumin a. Fat 
b. Citric acid b. Inorganic phos- b. Casein 
c. Potassium phate 
d. Sodium c. Calcium 
e. Chlorine d. Magnesium 
Bosworth and Van Slyke (1915) report the composition of cow’s, 
goat’s and human milk, shown in Table XXXVI. From this presenta- 
tion of the chemical composition of milk, it will be seen that it is an 
excellent medium for bacterial growth. 
Van Slyke and Bosworth (1914) studied the composition of milk 
serum after the other constituents had been removed by filtration 
through a Pasteur-Chamberland filter. The analysis of the serum is 
given in Table XX XVII. 
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