Conventionally pasteurized milk is not sterile it gets sterile after it is homogenized. The process of pasteurization involves sudden heating and sudden cowling of milk which does not kills all the microorganism but is intended to kill some of the bacteria and inactivates some enzyme.
Homogenization is a completely separate process which involve mechanical breakdown of fat molecules in the milk which increases the shelf life of milk by preventing the cream from rising at the top.
