10 CITY MILK SUPPLY 



casein and its salts with acids, forming compounds that dissolve easily 

 in water. Some of them are marketed as foods and patent medicines, 

 such as Plasmon, Nutrose, Sanatogen, Eucasein, Galactogen, etc. One 

 of the most characteristic properties of milk is the coagulation by the 

 enzyme contained in rennet. It is this that makes cheese manufacture 

 possible. The curd formed by the action of rennet is called calcium 

 paracasein. 



Lactalbumin. Lactalbumin makes up 15 per cent, or more of the 

 milk protein. It is held in solution in the milk serum but is partially 

 precipitated therefrom by heating to 158F. Lactalbumin is not acted 

 on by rennet nor is it coagulated by acids at ordinary temperatures. 



Lactglobulin. Lactglobulin is in solution in the milk serum but 

 exists only in traces. It is coagulated by heat at 161. 6F. but not by 

 rennet or acids. 



Carbohydrates. Lactose. The principal carbohydrate of milk is 

 the sugar, lactose. It is the specific product of the mammary gland 

 and is found only in milk. It has the symbol Ci2H 22 Oii-H 2 O and is 

 readily converted by bacteria into lactic acid, 



H OH 



H C C COOH. 



I 

 H H 



However, the conversion is not direct for the lactose is first changed by 

 enzymes into glucose and galactose from which the lactic acid is produced. 

 In the ordinary souring of milk several other bodies besides lactic acid are 

 formed by the breaking down of the milk sugar. 



Hexose Sugar. Jones, acting on a suggestion of Theobald Smith, 

 has recently reached the conclusion that there is a trace of hexose sugar 

 in normal milk and that it may come from the decomposition of lactose 

 into galactose, or more probably, may be derived from the cow's blood. 



Salts in Milk. The salts of milk have not been fully studied; sodium, 

 potassium, calcium, magnesium, chlorides, phosphates and sulphates 

 are commonly found, as well as traces of iron, citrates and salts of organic 

 acids. To some extent the salts are ionized. Some chemists express 

 the results of their analyses conventionally in the form of oxides, not 

 meaning to imply thereby that the mineral constituents actually so 

 exist in milk. Others state them in the form of hypothetical combina- 

 tions which are purely theoretical for how these constituents exist in 

 milk is not known. On burning milk, a white ash is left which does not 

 truly represent the mineral constituents for they are oxidized in the 

 operation. 



