Does Freezing Fish Kill Bacteria? Understand Bacterial Contamination in Fish

Does Freezing Fish Kill Bacteria

Many people choose seafood as a popular and healthy dish. But they may not know that different types of bacteria are found in seafood. To ensure food safety, it’s important to understand the potential risks of bacterial contamination, the sources and routes of contamination in fish. Is it true that bacteria will be destroyed when fish is placed in a freezer?  In this article, we will explore different types of bacteria found in fish as well as answer the question of whether freezing fish is a reliable way to kill microorganisms or bacteria.

Let’s get started and learn more about this important topic!

Understanding bacterial contamination in fish

Common bacteria found in seafood

Salmonella and Vibrio are two prevalent bacteria that cause bacterial contamination in fish. Salmonella is a type of bacteria that can cause human food poisoning. It is commonly present in animal intestines and can infect seafood via fecal matter or cross-contamination during processing.

In contrast, Vibrio bacteria flourish in warm coastal waters and can contaminate fish by exposure to seawater or seafood taken from affected locations. Vibrio infections can cause gastrointestinal problems and, in extreme situations, bloodstream infections.

Sources and routes of bacterial contamination in fish

Bacterial contamination in fish can occur in several phases, from pre-harvest through post-harvest. Pre-harvest contamination can occur from contaminated water sources or from fish being exposed to contaminated habitats. Overcrowded fish farms, for example, or those located near areas with low water quality, can increase the risk of bacterial contamination.

Inadequate handling procedures during the harvesting phase can introduce bacteria into the fish. If employees’ equipment, surfaces, or hands are not thoroughly cleansed and sterilized, bacteria can be introduced to the fish, resulting in contamination.

Bacterial contamination is also influenced by post-harvest conditions. Bacterial growth can be promoted in fish that are not preserved or transported under the correct conditions. Cross-contamination can occur when seafood is stored near raw meats or handled by people who have not practiced proper hygiene.

Risks associated with consuming contaminated fish

Consuming infected fish can pose a number of health hazards. Bacterial infections caused by contaminated seafood can cause diarrhea, stomach cramps, nausea, and vomiting. These infections can induce dehydration in extreme situations and necessitate medical attention. Pregnant women, young children, older adults, and anyone with impaired immune systems are especially vulnerable to serious complications from bacterial infections.

Additionally, some bacteria, such as Vibrio species, can cause more serious infections, such as wound infections and bloodstream infections. These infections can be fatal, especially in people with weaker immune systems.

It’s crucial to remember that while fully boiling fish can help kill many germs, it might not completely get rid of all pollutants, particularly poisons produced by specific bacteria. Therefore, reducing the dangers associated with consuming fish requires using proper handling, storage, and cooking techniques to prevent bacterial contamination.

We may take proactive actions to ensure the safety of the fish we eat by recognizing the prevalent germs present in seafood, the sources and pathways of contamination, and the risks involved.

Does freezing fish kill bacteria?

Fish is frequently frozen to extend its shelf life, preserve its freshness, and limit the risk of bacterial infection. However, when it comes to eliminating bacteria, it is critical to understand the limitations of freezing. Although freezing fish can lower the number of bacteria present, it may not completely remove all forms of bacteria.

Freezing works by decreasing the growth and activity of bacteria, allowing the fish to be preserved for a longer period of time. When fish is frozen at temperatures below 0°C (32°F), bacteria development is considerably suppressed, which can help avoid the multiplication of potentially hazardous microorganisms. In short, freezing fish will not kill bacteria, it will only put them in a hibernation state.

Pathogens such as Salmonella and Vibrio are among the most serious concerns about bacterial contamination in fish. These bacteria can cause foodborne diseases, putting customers’ health at risk. These germs can be reduced by freezing, although they may not be fully eliminated. Some bacteria strains are more resistant to cold temperatures and can survive the process.

Freezing will not kill bacteria, but only places them in a hibernation state
Freezing fish will not kill bacteria, but only places them in a hibernation state

What factors affect the efficiency of freezing?

The efficiency of freezing in killing bacteria is determined by a number of parameters, including the initial bacterial load, the type of bacteria present, as well as the length and temperature of freezing. While freezing can aid in bacterial growth management, it is not a replacement for good handling, cooking, and storage techniques.

Further reading:  Does Turning Off the Fridge Damage It?

It is critical to highlight that freezing does not eliminate bacteria-produced toxins. Some bacteria, like the Vibrio species, can create heat-stable toxins, which means they can resist cooking temperatures. Freezing fish infested with toxin-producing bacteria will not eliminate the poisons, and eating such fish may result in foodborne illness.

Tips to keep frozen fish in optimal conditions

  1. Freeze fish after purchase, as soon as possible.
  2. Wash the fish to remove scales and blood. It is also important to remove all internal organs.
  3. Dry the fish to remove moisture before freezing.
  4. Adjust the freezer temperature, you will definitely have it at -18ºC.
  5. Whole pieces? If you’re making grilled fish, like cod or eel, you can freeze the entire piece. If you know you’ll be baking it, we recommend cutting it before freezing it. This allows you to make smaller packages per serving and better use of the product.
  6. Plastic bags, aluminum foil, tupper… All of these products are suitable for freezing. Remember that the closure should be airtight.
  7. Date and type of fish. That’s what you’ll have to write in the package to have a more complete control. Fish can have it in the freezer, at -18ºC, for 6 months.

You may also like: Freezer Safe Plastic Containers

How to handle frozen fish properly

As mentioned above, it is critical to handle and store frozen fish properly to maintain its safety. To retain quality and reduce bacterial growth, fish should be frozen as soon as possible following harvest or purchase.

Furthermore, freezing fish at temperatures below -18°C (0°F) is recommended for better preservation and to effectively limit bacterial growth.

Also, it is important to thaw frozen fish in a regulated and safe manner. Because thawing fish at room temperature can promote bacterial growth, it is preferable to defrost fish in the refrigerator or under cold running water.

Refreezing previously thawed fish is not recommended since it increases the risk of bacterial infection.

Further reading: Is It Safe to Eat Freezer Burned Meat or Fish?


Does freezing fish kill parasites?

Parasites are endemic to aquatic environments. Therefore, fish infection is inevitable. In the seafood industry, people use freezing as a method to kill parasites.

Freezing can kill parasites if the food gets cold enough and stays that way long enough, according to guidelines for the food industry from the Food and Drug Administration.

What temperature kills parasites in fish?

Killing the parasites requires freezing the fish at an ambient temperature of:

  • Minus 4 degrees F or colder for seven days
  • Minus 31 degrees or colder until the fish is solid and store at the same temperature for 15 hours
  • Minus 31 degrees until the fish is solid and store at minus 4 degrees or less for 24 hours

Not all home refrigerator freezers are cold enough. To be sure your freezer will work for parasite control, use a good freezer thermometer.

Besides, F.D.A. also cautions that these techniques may not be suitable for particularly large fish that are more than six inches thick.

When cooking, most parasites are usually killed by thoroughly cooking food at 75°C or above (or 165°F).

Can Salmonella grow in frozen meals?

No. Salmonella will not grow in frozen meals; however, it can survive at freezing temperatures.

Besides, if food is thawed improperly (for example at room temperature), Salmonella will have a chance to grow.  It will not die if not thoroughly reheated at temperatures above 75°C.

Can cooking kill off bacteria?

Yes. You can cook the bacteria out of fish.

The favorable environment for bacteria to multiply rapidly is between 40 and 140 F degrees (danger-zone temperatures). The bacteria will not multiply but can begin to die between 140 and 165 degrees. When the temperature is above 212 degrees Fahrenheit (100 C degrees), the bacteria will die.


Bacterial contamination in fish is a major source of concern for food safety. Understanding the typical microbes found in fish, along with the sources and pathways of contamination, is critical for reducing the dangers of consuming infected fish.

While frozen fish can help lower bacterial levels, it is not a guaranteed means of eradicating all types of germs. To preserve the safety of the seafood we consume, appropriate handling, food preparation, and storage methods must be followed.

We can keep enjoying the advantages of fish as a nutritious and delectable dining option while limiting the potential health hazards by being aware and maintaining appropriate hygiene.

Jenny Brown
Hi, I’m Jenny. On my blog, you will find helpful advice about using and organizing the kitchen appliances. You will also receive the recommendations on choosing a compact refrigerator or freezer that best fits your demands. Besides, frozen meals from the freezer bring many incredible benefits because they ensure freshness, deliciousness, and full nutrients. Many helpful tips from experts on frozen meals will also be found.