528 THE CONTROL OF THE MILK SUPPLY 



had at any dairy supply at small cost. There are many such 

 mechanical coolers now in the market, allowing the milk to flow in 

 a thin layer over corrugated copper cylinders or coils, through 

 which is passing a current of cold water.^ 



Low temperatures, it is true, do not easily destroy life, but 

 they have a most beneficial effect upon the keeping quality of 

 milk. It has been suggested that at the outset of the process of 

 cooling, currents of air inimical to bacteria are started in the 

 milk. If the temperature be lowered sufficiently, the contained 

 bacteria become inactive and torpid, and eventually are unable 

 to multiply or produce their characteristic fermentations. At 

 about 50° F. (10° C.) the activity ceases, and at temperatures of 

 45° F. (7° C.) and 39° F. (4° C.) organisms are deprived of their 

 injurious powers. If it happens that the milk is to be conveyed 

 long distances, then even a lower temperature is desirable. 



The most important point with regard to the cooling of milk is 

 that it should take place at once. It must not be forgotten that 

 cooling processes are not sterilising processes. They do not 

 necessarily kill bacteria ; they only inhibit activity, and under 

 favourable circumstances the torpid bacteria may again acquire 

 their injurious faculties. Hence, during the cooling of milk, 

 greater care must be taken to prevent aerial contamination than 

 is necessary during the process of sterilising milk. The cooling 

 apparatus should be kept clean, and the cooling carried out under 

 clean and proper conditions. Climate makes little or no differ- 

 ence to the practical desirability of cooling milk, yet it is obvious 

 that less cooling will be required in the cold season. 



Transport. — When ready for transport to the town, the milk, 

 screened and cooled, should be placed in sterilised churns which ^ 

 should be locked or sealed. The objects gained by careful sealing! 

 will be twofold, viz., there will be no opportunity for the admission} 

 of dirt and dust to the milk, and there will be no mixing of the 

 milk at railway stations. Consignors and vendors have frequently 

 alleged that railway companies will not transmit sealed churns. 

 This is incorrect.^ 



* Appliances of this kind may be obtained from Lawrence & Co., 22 St 

 Mary Axe, London, E.C., and 132 Latimer Road, London, W. ; the Dairy 

 Supply Company, Limited, 28 Museum Street, London, W.C.; R. A. Lister & 

 Co., Dursley, Gloucestershire ; or any other good firm. 



'■^ The evidence given before the Departmental Committee on Milk included 

 a letter dated 29th May 1899, in which the Assistant Secretary of the Board 

 of Agriculture inquired of the Railway Companies' Association, through the 

 Board of Trade, if it was their practice to require milk churns to be unlocked. 



