MILK AND MILK PRODUCTS 3 



cause it is not sure that the samples were of average character 

 or the methods of analysis accurate : 



HUMAN. 



Fat, 3.5 



Sugar, 6.8 



Proteids, i .5 



Ash, 0.2 



12.0 13.0 9.3 13.5 10.4 15.8 



Normal milk is an opaque white or yellowish-white fluid, 

 with an odor recalling that of the animal, and a faint sweet 

 taste. The opacity is due largely but not entirely to the fat 

 globules. The reaction of freshly drawn milk to litmus is 

 usually alkaline, but is sometimes amphoteric; that is, it turns 

 the red paper blue and the blue paper red. The specific gravity 

 varies between 1.027 and 1.035. ^ usually undergoes a gradual 

 augmentation (sometimes termed Recknagel's phenomenon) 

 for a considerable time after the sample has been drawn. The 

 increase may amount to two units (water being 1000). The 

 specific gravity becomes stationary in about 5 hours if the milk 

 be maintained at a temperature below 15, but at a higher 

 temperature it may require 24 hours to acquire constancy. The 

 change is not entirely dependent on the escape of gases. 



Unless collected with special care and under conditions of 

 extreme cleanliness, milk always contains many bacteria and 

 animal matter of an offensive character, such as epithelium, 

 blood and pus cells, particles of feces, and soil. 



At ordinary temperature milk soon undergoes decomposition, 

 by which the milk sugar is converted principally into lactic acid, 

 and the proteids partly decomposed and partly coagulated. 

 The liquid becomes sour and the fat is inclosed in the coagu- 

 lated casein. In the initial stages of decomposition the proteids 

 frequently undergo transformations into substances which are 

 the cause of the violent poisonous effects occasionally produced 

 by ice-cream and other articles of food into the preparation of 

 which milk enters. 



