2 MILK ANALYSIS 



but colostrum may contain as much as 8 per cent. It is co- 

 agulated on heating. 



Lactose. — This is a sugar peculiar to milk. 



Citric acid is a normal constituent of the milk of various 

 animals. In human milk, the quantity is about 0.5 gram to 

 the liter; in cow's milk, from i to 1.5 grams. It is not de- 

 pendent on the citric acid present in the food. 



Wender states that the following enzyms exist in normal milk : 



Milk trypsin or galaciase. This is a pi-oteolytic enzym. It 

 dissolves casein and is rendered inactive by exposure to a tem- 

 perature of 76°. 



Milk-catalase. This can decompose hydrogen dioxid and 

 similar compounds. It is rendered inactive by exposure to a 

 temperature of 80°. 



Milk-peroxydase, an anaerobic oxydase, that is, a body that 

 has the power to decompose peroxids and carry the oxygen 

 over to other substances. This is the substance which produces 

 the reaction when- milk, hydrogen dioxid and tincture of guaia- 

 cum are mixed, by which a deep blue is obtained. This enzym 

 is rendered inactive by exposure to a temperature of 83°. 



Minute amounts of nitrogenous bases occur in milk. 



Mineral Matter. — The ash of milk contains calcium, mag- 

 nesium, iron, potassium, and sodium as chlorids, carbonates, 

 sulfates, and phosphates. It does not exactly represent the 

 salts present in milk. 



Richmond has determined the ratio of the ash to the solids 

 not fat of 135 samples of milk. This was found to range from 

 7.8 to 9.4 per cent., but more usually from 7.8 to 8.5 (average 

 8.2) per cent. Many ashes were alkahne to turmeric, litmus, 

 and phenolphthalein, the maximum alkalinity being 0.025 per 

 cent, calculated as sodium carbonate. 



The following table gives the approximate composition of 

 some milks. Analyses of the milks of less important animals 

 have been published, but the figures are of uncertain value, be- 



