One of the great benefits of freezing food is that it needs no preservative. The freezing itself is the preservative. As long as food is kept at 0°F or less, then there is no way for microbes (the things that make people sick) to grow. The microbes that were on the food will not die, but they will not keep multiplying. However, it is important to understand that once food is taken from the freezer the microbes will start to grow again. They grow at the same rate as they do on unfrozen food. Therefore, if food needs to be defrosted before eating or cooking, it should be defrosted in the refrigerator.