CLEANING AND THE PROCUREMENT OF MILK 55 



water should, however, not be used too warm to begin with, or the 

 proteins will be rendered insoluble. It is well-known that cheese 

 cloth quickly becomes stiff and useless if not rinsed in cold water 

 before washing in boiling water. By the use of soda or lime, the 

 casein is dissolved and the fat is emulsified, 'i.e., reduced to a fine 

 state of division. These chemicals also act as poisons towards 

 bacteria, i.e., disinfectants. They are most effective if used 

 together, but unfortunately tinned vessels do not stand this 

 treatment well. Soda is to be preferred to lime for the cleaning 

 of such vessels, for though it is somewhat more energetic in its 

 action on tin, it removes fat more readily. In order to prevent 

 the tinning on pasteurisers from being attacked, it is best to soak 

 the crust which has formed in a cold solution of soda, whereupon 

 it will easily be removed on scrubbing with clean warm water. 

 The plates of centrifuges may be cleaned in the same way. With 

 lime, the fat forms insoluble lime soaps which makes the tin dull 

 and rough. On the other hand, lime is to be preferred for wood 

 work, partly because if rubbed in as milk of lime it will remain 

 where it is for some time, so that its disinfecting action will be 

 prolonged, and partly because the lime soaps fill up the pores and 

 render the surface of the wood smoother and firmer. The cleaning 

 must be finished with several rinsings with plenty of water, or 

 some of the chemicals and dissolved dirt will remain behind. 

 The last rinsing should be with hot (sterile) water to ensure rapid 

 drying. Wood easily frays with too much heating, but good wood 

 will stand liberal quantities of pure warm water and even steam ; 

 churns are best cleaned by simply rinsing repeatedly with water 

 at 90 C. Tinned or other metal vessels should if possible be boiled 

 out or steamed as a final treatment, thus ensuring an extra 

 sterilisation and rapid drying. This last point is a very important 

 one, for in spite of all reasonable care absolute cleanliness and 

 sterility are seldom achieved, but if only the vessels are dried as 

 soon as possible, no new vegetation will be allowed to develop in 

 them. Wherever possible, make the best use of direct sunlight, 

 which both dries and sterilises. Wind and through draughts are 

 also useful provided that they bring no dust. All that has been 

 said regarding pails, apparatus and piping applies equally well to 

 the cloths and scrubbing, brushes used in cleaning ; these must be 

 thoroughly cleaned and finally scalded with boiling water and 

 dried to prevent them becoming slimy ; they may conveniently 

 be dried in the boiler room. Every dairyman should clearly 

 understand that cloths and brushes may do more harm than good 

 if not perfectly clean. It is well known that cleaning cannot be 

 effective if the vessels have inaccessible corners or rough surfaces ; 

 frayed woodwork or rusty pails should therefore not be tolerated. 



