Normally, there should be no preservatives added to canned food. Canned food is preserved by first sealing it, then heating and sterilizing it to completely kill microorganisms in the food. After a certain period of time, the microorganisms in the cans are killed; at the same time, because they have been sealed, the microorganisms in the environment can not enter the cans. Because of the control of microorganisms, the canned food can be preserved for a long time and does not need preservatives.