j642 The Cornell Reading-Courses 



facture of proprietary foods, and in pharmacy for coating pills and making 

 powders. The manufacture of milk sugar is an expensive process and 

 is carried on only where large quantities of skimmed milk or whey are 

 available. 



Milk sugar is of great importance in dairy manufacturing because 

 the acid in milk and cream is produced from it and we have come to like dairy 

 products the flavor of which is affected by the formation of this acid. 

 The public demands a butter made from cream soured with lactic acid. 

 In the manufacture of American cheddar cheese the amount of acid formed 

 at different stages in the process of manufacture greatly affects the kind 

 and quality of the product. 



Lactic acid, as found in milk, is made by the action of lactic-acid 

 bacteria on milk sugar. These bacteria, or germs, are found nearly 

 everywhere in external nature, and occur on the body of the cow, on the 

 dust in the air, and on the clothing of the milker. Unless precautions 

 are taken these germs get into the milk, and under conditions favorable 

 to them they multiply rapidly and cause the milk to sour. The chem- 

 ical reaction that takes place is given as follows: 



Milk sugar = lactic acid 

 C12H22O11 • H2O = 4C3H6O3 



Milk sugar is found nowhere in nature except in the milk of animals of 

 the class known as Mammalia. 



Albumen 



Albumen is a nitrogenous substance in solution in milk; being in solu- 

 tion, it is easily digestible. In composition it may be compared to the 

 white of egg. It is precipitated by heating to about 160 to 170 F., and 

 when once thrown down it will not go into solution again. The fact that 

 albumen is precipitated by heat is the reason why milk utensils, when 

 cleaned, should be first rinsed in cold water. If hot water is used first 

 the albumen is precipitated on the utensil, and, being sticky, is difficult 

 to remove. If there are cracks or seams in the utensil some of the precipi- 

 tated albumen lodges in these; and since albumen is an excellent food for 

 bacteria the utensil soon becomes a source of contamination for all milk 

 that comes in contact with it. 



Albumen has one commercial use — in the manufacture of Italian cheese. 

 This cheese is made where large quantities of whey are obtainable. The 

 whey is heated to a high temperature, which precipitates the albumen. 

 The albumon is allowed to collect, the whey is then drawn off, and the 

 albumen is drained and dipped into molds. This cheese is more or less 

 tasteless since there is very little flavor to albumen ; but it is very nutritious. 



