lo GENERAL CONDITIONS AFFECTING BACTERIA IN MILK 



naked eye appearance of surface bubbling. In the experiments in 

 question, the temperature was taken by independent individuals at 

 the moment of the supposed boiling milk being taken off the fire 

 by the cook. In only one case did the temperature exceed 90'' C. 



Milk scalded as above has a pronounced odour and flavour, 

 and the temperatures at which milk heated with ordinary pre- 

 cautions against burning, etc., changes in odour and flavour we 

 found to be as follows : — 



Up to 80° C . . No perceptible change. 



Between 80° and 85° . A slight change in odour and flavour can be perceived. 

 Between 85° and 90° . A decided scalded flavour and odour becomes perceptible. 

 At 90° . . . The flavour and odour are pronounced, and become accentuated 



as the temperature rises to 100" C. 



A noteworthy point with regard to the above is that the 

 resultant cream from the heated milk undergoes no change in 

 flavour unless the milk temperature has exceeded 90° C. 



It should also be noted that milk heated in an ordinary pan 

 begins to change flavour at a lower temperature than if heated in 

 a water-lined pan such as is now in frequent use for milk purposes. 



The objections on the part of the public to boiled milk as an 

 article of food are chiefly the following : — 



1. That milk so treated has distinctly a " cooked " taste. 



2. The formation of surface scum on the milk. 



The former it is difficult to avoid altogether when milk is heated 

 to a temperature above 80° C, but the latter, being an oxidation 

 product, can be almost wholly avoided by the simple expedient of 

 not exposing the boiled milk to the air until it has cooled down to 

 below 60° C. 



If the following simple rules are observed in heating milk, the 

 change in flavour will be but slight, and the formation of surface 

 scum practically nil : — 



1. Use an ordinary double milk-pan, or a smaller covered sauce- 

 pan containing the milk placed inside a larger one containing the 

 water. 



2. Let the water in the outer pan be cold when placed on the fire. 



3. Bring the water up to boiling point, and maintain it at this for 

 three or four minutes without removing the lid of the inner milk-pan. 



4. Cool the milk down quickly by placing the inner pan in one 

 or two changes of cold water without removing the lid. 



5. When cooled down aerate the milk by stirring well with a spoon. 

 Boiling milk does not materially affect its power of clotting in 



the stomach, nor does it materially affect its digestibility (Cautley). 



