22 MILK AND DAIRY PRODUCTS PART 



into a measuring cylinder and exactly measured ; suppose in 

 this case the volume to be 205 c.c., if from this the 20 c c. of 

 added ammonia be deducted, there remains 185 c.c. as the 

 amount of milk originally present in the bottle. Specific 

 gravity, percentage of fat, &c., can then be determined in the 

 usual way in this mixture of milk and ammonia, and the 

 results calculated to the original volume of milk. 



This method cannot, however, be applied if the coagulated 

 milk is very old, for in sour whole milk the fat gradually 

 undergoes decomposition, so that an estimation of the fat then 

 becomes unreliable. Separated milk and buttermilk, on the 

 other hand, are much more stable, and it is possible with the 

 help of Weibull's method to analyse very old samples of these 

 two sorts of milk with good results. 



(B.) PHYSICAL EXAMINATION. 



The purely external indications that milk is normal and 

 fresh are its appearance, taste, and smell. 



In appearance the milk must be a completely homogeneous, 

 opaque liquid which, on standing, must give a homogeneous arid 

 sharply defined layer of cream. 



The presence of flocculcnt matter in the milk points either 

 to some disease in the cow, such as inflammation of the 

 mammary gland, or to the milk being so old that changes due 

 to micro-organisms have taken place. The colour of milk 

 should be that of porcelain; it can, however, have either a 

 yellowish or a bluish fcnge, according to the amount or colour 

 of the contained fat. A reddish tinge is indicative of blood 

 from the udder, from which it may be concluded that this 

 organ has been injured in some way or the other. In excep- 

 tional cases the red colour may come from such foods as 

 mangels, beets, carrots, &c., or from colostrum milk. 



Milk should have a pleasant, characteristic, sweet taste ; any 

 sourness indicates an advanced stage of lactic acid fermentation. 



A bitter or salty flavour is sometimes found in milk from 

 cows which are practically dry or are suffering from some 

 disease of the udder. It may arise also from the action of 

 peptonising bacteria upon the protein of the milk, whereby 

 substances (peptone) with poisonous properties are formed. 



