CHAPTER V. 



FOODS. 



EXAMINATION OF MILK. 



AVERAGE composition of cow's milk : Water, 87 to 88 % ; 

 proteid, 3 to 3-5 % ; fat, 3-5 to 4-5 % ; sugar, 4 to 5 % ; 

 mineral matters. 0-7 %. 



Physical Characters.- Placed in a narrow glass it 

 should be quite opaque, of full white colour, without 

 deposit, without peculiar smell or taste, and when boiled 

 it should not change in appearance. The temperature 

 should be taken. 



Reaction. Should be slightly acid, or neutral, or very 

 feebly alkaline. Fresh milk is sometimes both acid and 

 alkaline to indicators, that is, amphoteric, turning red 

 litmus blue and turmeric to brown. Strongly alkaline : 

 cow ill, or much colostrum, or addition of sodium carb. 

 Strong acidity : lactic or butyric acids, and indicative of 

 retrograde change. 



Cream. Stand 100 c.c. in a measure for twenty-four 

 hours in a still atmosphere. Read off proportion of cream. 

 Should be T ^ to T y^ ; generally about y^. Alderney cows 

 give -j 3 ^ to -jffy. Time of year and breed to be considered. 



Specific Gravity. At 15 C. or 60 F. Varies from 

 1027 to 1034, being less as fat is greater. The specific 

 gravity is raised by skimming and can be reduced by 

 adding water, so that this factor alone is not a reliable index 

 to the character of a sample. The specific gravity falls 

 i for each rise of 10 F. above 60, and at 60 F. there 

 is a loss of 3 of specific gravity for every 10 per cent of 

 water added. 



Three methods Specific gravity bottle, lactometer, and 

 Westphal balance. 



Total Solids. Ought not to be below 11-5 per cent ; 

 but are more usually 12 to 13 per cent. Take 2 c.c. of the 

 milk in a flat shallow dish of known weight. Evaporate 

 to dryness over the water-bath, and then in the water-oven 



