2 8o MILK AND ITS HYGIENIC RELATIONS 



Savage gives some interesting experiments upon the tempera- 

 ture of milk in churns on its way to the customer. These experi- 

 ments demonstrate the importance of a thorough cooling on the farm 

 in view more especially of the absence of cooling facilities later on. 



In the first experiment the milk in the churn was warmed until 

 the temperature after stirring reached 37*6 C. The milk was then 

 sent out in the milk cart, covered with an ordinary canvas churn 

 cover to protect it from the direct rays of the sun, and was driven 

 all over London. It left the dairy at 11.30 A.M., the temperature 

 of the air being 19 C. It returned to the dairy at 4 P.M., the air 

 temperature being then 21 C. The temperature of the milk, how- 

 ever, had only fallen to 30-8 C. 



In the next experiment the initial average temperature of the 

 milk was reduced to 6-4 C. It left the dairy at 11.40 A.M. under 

 similar conditions to the above. The initial air temperature was 

 then 18-6 C. The milk was brought back to the dairy at 4 P.M., 

 the air temperature being then 21 -6 C. The temperature of the 

 milk, however, was only 10*8 C., that is to say, in four and a half 

 hours the temperature of the milk had only been increased by 

 4.4 C, although the air temperature throughout was much higher. 



Evidently the alterations in the temperature of milk take place 

 very slowly, owing no doubt to slowness of convection. 



The milk, after cooling, should be at once run into sterile 

 receptacles. If into bottles, these should have been washed in 

 hot water and soda, and after satisfactory rinsing should be 

 exposed to the action of steam, and be kept mouth downwards 

 until required for the next service. These bottles should be sealed 

 on the farm at once, after filling, by means of a cap, and if considered 

 desirable by means of some apparatus which will show whether the 

 bottle has been kept intact or whether it has been opened after rilling. 

 This last is insisted on by the American Medical Milk Commissions. 



After the milk has been bottled it should be transported cool 

 to the dairyman and delivered cool to the customer. 



The apparatus used lor bottling is shown in Plate V. The 

 milk passes straight from the cooler to a tank, with numerous 

 small pipes leading to bottles which are placed one below each 

 pipe. An arrangement exists which allows a definite quantity 

 of milk to pass into the bottles, according to the capacity of the 

 bottles. As soon as the e are filled the milk flow stops and the 

 whole tray with the bottles can be pulled to an adjacent platform, 

 where they are at once covered. 



Milk sent in churns from the farm must be subsequently bottled 

 by the dairyman, or be taken round in the churn and delivered in 

 small quantitie to the customers. 1 At every stage of its manipula- 



1 The contamination arising from the entry of dust through the so-called 

 ventilation holes in the lids of churns, and the risk of contamination from 

 manipulation on the journey or at the dairy are too well known to require 

 further mention here. 



