Answer:
Pasteurization of the orange juice is necessary in order to inactivate the enzymes present in the orange juice. It also destroys the harmful microorganism found in the juice which spoils the juice.
Enzyme activity leads to the loss in the single strength and gelatin in the concentrated orange juice. The relevant enzymes that is found in the juice requires more heat to get inactivated.
This heat destroys the vitamin C found in the juice while it is concentrated.