Does freezing kill bacteria?

In this brief guide, we will answer the query, “Does freezing kill bacteria?”. We will also discuss how freezing harms bacteria, how these bacterias survive freezing, and whether freezing kills viruses.

Does freezing kill bacteria?

No, freezing doesn’t kill bacteria. Instead, it will go into a dormant state or hibernation. These bacterias are not dead, they stay alive within the frozen food. They stay inactive until they are thawed and brought back to room temperature. The most common bacteria E.coli survive any freezing temperature in the home appliances.

Although some bacteria are said to be killed when exposed to very harsh temperatures, this is not possible in your daily life as your home refrigerator has a limited temperature range which is not capable of killing bacteria. 

While it is true that freezing food at 0 °F inactivates any germs, bacteria, yeasts, or molds present, if frozen, these germs can become active again, multiplying to levels that can cause foodborne illness under favorable conditions. 

Since these thawed bacterias will then proliferate at roughly the same pace as bacteria on fresh food, they must be dealt with just like any perishables. The FDA encourages thawing frozen goods in the refrigerator so that even after they defrost, they do not surpass the room temperature danger zone.

How does freezing harm bacteria?

Although freezing bacteria in your average refrigerator is not enough to kill bacteria, it may harm or even kill the bacteria in the process of freezing and unfreezing. It is said that the temperature should be 80 degrees Fahrenheit below the freezing point to actually kill the bacteria by freezing.

Rigid ice crystals are formed when you expose the bacteria to cold temperatures. This may destroy some structures of bacteria like cell walls and internal structures including DNA. Furthermore, when water freezes, it expands, which might cause the bacterium to rupture.

More bacterial deaths occur due to the damage they face during repeated freezing and thawing than by the low-temperature exposure itself.

It is also important to note that bacteria as well as many other pathogens have their repair mechanisms, and some species can repair their disrupted DNA even at extremely low temperatures. Furthermore, certain microorganisms produce specific proteins that prevent the development of ice crystals, allowing water to remain liquid around them.

Also, many more known and unknown actions occur during freezing that may harm microorganisms. As a result, cold temperatures can be dangerous to bacteria in a variety of ways.

How do bacteria survive freezing?

Most of the bacteria survive freezing by going into a dormant state or hibernation. They enter an inactive phase and cease all metabolic activities. This is actually their defense mechanism to stay safe from the freezing temperature. 

During this state, they cannot cause any harm to the food since all their activities are halted, but as soon as they come out of hibernation, they go back to normal or are even more active than before. Bacteria can survive for a very long time in this phase and then simply return to a normal form when they are exposed to the normal room temperature. 

That is when the environment becomes favorable for bacterial growth. They will multiply really fast under favorable conditions. So the foods aren’t safe even after freezing. In fact, after thawing, they are more susceptible to bacterial infections.

Does freezing kill viruses?

No, freezing doesn’t kill viruses either. Most viruses are also not killed by cold temperatures. You may have heard that chilly winter temperatures create viruses like influenza or the flu. This is just a misconception, but a 2014 analysis of evidence by a Ph.D. candidate at Harvard University revealed that influenza thrives in cold regions. 

This virus appears to spread more effectively at colder temperatures with lower humidity levels. At 43 degrees Fahrenheit, influenza may survive for around 23 hours. Viruses are killed or eliminated by heat rather than cold as they require a moist environment to survive. 

This is why viruses are more communicable on nonporous metallic and plastic surfaces than on porous things such as soft toys, cloth, and wood. For more details, please click the link here.


In this brief guide, we have answered the query, “Does freezing kill bacteria?”. We have also discussed how freezing harms bacteria, how these bacterias survive freezing, and whether freezing kills viruses.