Milk and Its Products. 270 



sometimes find their way into milk. Outbreaks of diarrhoea, ty- 

 phoid and cholera have been traced to contaminated milk. It has 

 also been shown that milk can act as a carrier of tuberculosis. 

 Milk, too, has the property of absorbing gases and vapors and in 

 consequence readily acquires odors and flavors from the air. 



All these facts emphasize the necessity of cleanliness in milk 

 production and precautionary measures to check bacterial devel- 

 opment should the milk become seeded. Their growth can be 

 checked by cooling the milk as soon as it is produced. This pre- 

 vents a rapid development of the organisms already in the milk, 

 but will not entirely prevent their development. It will prolong 

 the sweetness of the milk. In order to destroy the organisms 

 which have gained access to the milk, heating or the use of anti- 

 septics must be resorted to. Where the process of heating is 

 carried on at a temperature high enough to completely destroy 

 all organisms and their spores a process known as sterilization 

 and requiring a temperature above 100 C. undesirable chem- 

 ical changes are produced in the milk. The sugar is turned 

 brown, the albumin partly precipitated, and the milk acquires a 

 burnt or cooked flavor. To avoid these disadvantages the process 

 known as Pasteurization is often substituted. The milk is heated 

 to only 60 to 80 C., whereby the flavor is little affected and most 

 of the active bacteria are killed. The keeping qualities are thus 

 materially increased. 



Antiseptics. By adding various substances to milk, the 

 growth of micro-organisms can be impeded, if not entirely pre- 

 vented. When, however, such quantities of an antiseptic are 

 added as will prevent bacterial growth, then there is little doubt 

 that the milk is made unsuitable for human consumption. The 

 chief preservatives in common use are boric acid, salicylic acid, 

 formaldehyde and benzoic acid. Their use in any quantity is 

 reprehensible, allowing uncleanly methods in milk production to 

 be practiced, as well as endangering the health of the consumer, 

 and should be absolutely prevented. 



