It is generally accepted that clean milk means milk which is free 

 from microorganisms or the products of their action. It is possible 

 to conceive of milk being impure from something other than micro- 

 organisms or their products, such as the addition of some poisonous 

 substance to milk. The possibility of such contamination is, however, 

 so rare and so remote that the words "impure milk," have come to 

 mean that which is affected by the action of microorganisms. 



For this reason all operations and experiments performed in a 

 laboratory should be done in such a way as to prevent bacterial con- 

 tamination, and all dairy utensils with which the milk comes in con- 

 tact should be rendered sterile so far as possible. This can be done 

 by thoroughly scalding all dairy apparatus, or better still by 

 exposing them to live steam for not less than one hour. If the 

 dairy utensils are scalded by means of hot water, the temperature of 

 the water should be not less than i8oF. and it should be as near the 

 boiling point as possible. 



Dippers and other dairy utensils in which milk is handled, or which 

 comes in contact with the milk in any way, should not be laid on the 

 floor and then placed in the milk. Care should be taken not to touch 

 the surfaces of dairy utensils, such as coolers, bottle fillers and so 

 forth, with the hands. Water even in small amounts, may, if allowed 

 to enter milk, cause it to putrefy. 



CLEANING DAIRY UTENSILS 



Dairy utensils must be thoroughly cleaned if milk is to be handled 

 in a sanitary manner. The proper way in which to clean a dairy 

 utensil is to first rinse it with cold or luke-warm water, preferably the 

 latter. This removes most of the milk from the utensil and prevents 

 later cooking of the albumen of the milk on to the apparatus, when it 

 is scalded or sterilized. The utensil should next be thoroughly washed 

 by means of a brush and hot water in which there has been dissolved 

 some good washing powder. An excessive amount of powder is not 

 necessary, a tablespoonful to a pail of hot water is usually sufficient. 

 The utensil should then be scalded in hot water, and if possible, 

 exposed to the action of live steam for not less than one hour, thereby 

 rendering the utensil as sterile as possible. It should be kept in a 

 place where it will not become recontaminated. 



