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What is Temperature used for Pasteurisation is: and explain in detail?
Ref. Textbook of Microbiology and Immunology BY Parija. Page.  25
 
Pasteurisation

Pasteurization is not the same as sterilization.
Its purpose is to reduce the bacterial population of a liquid such as milk and to destroy organisms that may cause spoilage and human disease.
Spores are not affected by pasteurization. 
The intent of pasteurization of milk is to eliminate pathogenic microbes. It also lowers microbial numbers, which prolongs milk's good quality under refrigeration.
the milk was exposed to a temperature of about 63C for 30 minutes, called the holding method. 
Modern pasteurization - uses higher temperatures, at least 72C, but for only 15 seconds.