Does Freeze Drying Kill Bacteria?

Milosh Potikj | July 17, 2023 | 9 MIN READ

Are you worried about the safety and freshness of your food, especially in uncertain times? To make informed decisions about food safety, it's important to understand freeze-drying and other food preservation methods. Knowing the science empowers you.

In this article, we will explore the effectiveness of freeze-drying. It can keep food safe from bacteria and help it last longer. By preserving its nutritional value, you can have peace of mind knowing that your food will be both safe and nourishing.

What is Freeze Drying?

What is Freeze Drying?

Freeze drying is a method to remove moisture from different things, like food, to keep them fresh. This process involves three main steps: freezing, primary drying, and secondary drying.

Freeze drying removes the water content of a product without passing through the liquid phase. The first step involves freezing the product to a very low temperature. In primary drying, the frozen water goes directly from solid to gas without becoming liquid. Preserving the product's nutritional value, taste, appearance, and heat-sensitive compounds is very important.

After primary drying, the frozen product undergoes secondary drying. In this step, we remove more moisture from the product. This makes it last longer and reduces the risk of bacteria.

Freeze-dried foods retain their original shape and texture once rehydrated. This method preserves food for a long time without affecting its taste or quality. Freeze-drying is commonly used to make freeze-dried foods like pet food, fruits, veggies, and dairy.

More: The Best Freeze Dryers For Drying Food At Home.

What Bacteria Reacts to Freeze Drying?

Freeze drying is a way to keep food fresh for longer by taking out the water. It also makes it less likely for bacteria to grow. Freeze drying can kill bacteria, but some bacteria can resist it.

Certain bacteria, such as E. coli, Yersinia, Campylobacter, and Salmonella, can survive freeze drying. These bacteria have resistant cell membranes. The bacteria have a tough layer that helps them survive freezing and drying.

One such factor is the presence of fatty tissue. Bacteria in fatty tissues are harder to freeze dry because fat protects them. Where the bacteria are in the food can affect how they react to freeze drying.

To illustrate the bacterial response to freeze drying, let's take the example of the Harvest Right 4-tray Medium Home Freeze Dryer. This freeze dryer takes out water from different types of food, like fruits, vegetables, and pet foods. Freeze drying can reduce bacteria, but it may not get rid of all, especially resistant bacteria.

More: Things To Know About The Harvest Right Freeze Dryer.

Does Freeze Drying Kill Bacteria?

Does Freeze Drying Kill Bacteria?

Freeze dryers are used to preserve food by removing water, preventing bacteria and spoilage. This substance is commonly used for freeze-dried foods like dog food and other products. It helps them last longer on the shelf and when stored for a long time. To make sure food is safe, it's important to know how freeze drying affects bacteria. We need to understand this to handle food properly.


Before freeze drying raw meat, it is important to cook it first to remove harmful viruses. If you freeze-dry raw meat without cooking it first, the viruses can go into hibernation instead of getting killed. This is a problem because when rehydrated or eaten by a host, the viruses can become infectious again.

Cooking meat before freeze drying is very important. High temperatures above 140°F (60°C) can effectively kill most viruses, including those that cause food poisoning. When we cook raw meat, the viruses in it are destroyed. This makes freeze-drying safer for the final product.

To keep food safe, follow proper ways to handle and cook it before freeze drying. By doing this, the chance of viral contamination can be greatly reduced. This allows for the production of safe freeze-dried products.

Harvest Right Freeze dryers are a perfect solution for your food.


Some foods, like freeze-dried products, can have parasites that may harm your health. Freezing temperatures can deactivate parasites during freeze-drying, but it doesn't always eliminate them.

To freeze dry food, first freeze it at very low temperatures. Then, remove the frozen water by sublimation. This can kill certain parasites that are sensitive to cold temperatures. However, other parasites may not be completely eradicated through freeze drying alone.

To make freeze-dried foods free from parasites, use proper cooking techniques. Cooking at 140-167 degrees Fahrenheit for 15-30 minutes is the best way to get rid of parasites. The temperature range kills any remaining parasites, ensuring the safety of the food.



Salmonella is a big worry with freeze drying and making food safe. This foodborne pathogen is responsible for causing considerable cases of food poisoning worldwide. When food is freeze-dried, it can become contaminated with bacteria like Salmonella, which is harmful.

Processed foods, like freeze-dried products, can get Salmonella if raw ingredients are infected or handling is unhygienic. It can also happen during production. If not treated well, these bacteria can survive freeze-drying and make people sick if eaten.

The risks associated with Salmonella contamination in freeze-dried foods are significant. Consuming contaminated products can lead to symptoms such as diarrhea, abdominal pain, fever, and vomiting. In the worst cases, it can lead to hospitalization. In very rare cases, it can be deadly, especially for people with weak immune systems.

Effectiveness in Killing Bacteria

Freeze drying is an effective method for killing bacteria in food products. The freeze-drying process starts by freezing the food. Then, the water content is removed through sublimation. Sublimation is when frozen water turns into a gas without becoming liquid first. Drying food prevents bad bacteria from growing and lowers the chance of making people sick.

Freeze drying usually kills most bacteria, but some types are more resistant to it. Factors such as the composition of the bacteria and the food being freeze-dried can influence its effectiveness. Certain types of bacteria, such as Bacillus and Clostridium, are harder to freeze dry because of their strong spore shells.

The Harvest Right Stainless Steel X-Large freeze dryer is often chosen for freeze-drying food. It can freeze dry raw and frozen foods, pet foods, and dairy and egg products. The freeze dryer kills harmful bacteria. It does this during the freeze-drying process. This allows for safe long-term storage. It works for a variety of food items.

Read More: Grow With Remo Nutrients

How Can I Reduce the Number of Bacteria?

How Can I Reduce the Number of Bacteria?

Freeze drying preserves food by removing water, extending its shelf life. One of the key concerns when it comes to food safety and preservation is the presence of harmful bacteria.

Practice Handwashing

Proper hand hygiene is of utmost importance when it comes to freeze drying food. To make food last longer and keep it nutritious, we eliminate water from it. However, without practicing proper handwashing, the risk of bacterial contamination increases significantly.

Handwashing is a crucial step in preventing the spread of harmful bacteria and other pathogens. It gets rid of bacteria on the hands that could contaminate the freeze-dried products. The process involves using warm water and soap, lathering for at least 20 seconds, and thoroughly rinsing and drying the hands.

Prevent Cross Contamination

When freeze-drying, it's important to prevent cross-contamination while handling raw food. Here are the steps and precautions to follow:

  1. 1. Separate raw and cooked foods: Keep raw and cooked foods apart throughout the freeze-drying process. This includes handling, storage, and processing to prevent the transfer of harmful bacteria.
  2. 2. Clean hands and workspace: Before working with raw food, ensure that your hands are thoroughly washed with soap and warm water for at least 20 seconds. Additionally, use disinfectants meant for food areas to clean and sanitize the workspace.
  3. 3. Wash utensils, trays, and surfaces: Wash all utensils, trays, and surfaces that come into contact with raw food before and after each use. Use hot, soapy water and scrub them to remove any residual bacteria.
  4. 4. Use separate cutting boards: To prevent cross-contamination, use different cutting boards for raw and cooked foods. This applies to both meat and non-meat products.
  5. 5. Store raw food properly: Raw food should be securely wrapped and stored in airtight containers to prevent bacterial contamination. Keep it separate from ready-to-eat or cooked foods in the freezer to eliminate any chances of cross-contamination.

To keep food safe when freeze-drying, follow these steps to avoid cross-contamination and sickness.

Read More: How Long Does It Take To Turn Ozone into Oxygen?

Keep A Stable Storage Temperature

Keep A Stable Storage Temperature

To keep freeze-dried food in optimal condition, it is crucial to store it at a stable temperature. Freeze-drying takes out water from food, keeping its texture, flavor, and nutrients intact. It works well for storing food for a long time. To keep food safe, it's important to store it correctly and prevent germs from growing.

It is recommended to store freeze-dried food between 0°F (-18 °C) and 20°F (7°C) to ensure its quality and extend its shelf life. When it's cold, it's harder for microbes and pathogens to grow and multiply.

If freeze-dried food gets too hot, it can have bacteria in it and make you sick. When it's warm, bad bacteria grow and spread in food, making people sick.

Read More: How Hydroponics is Helping End World Hunger


Does freeze drying destroy enzymes?

Enzymes are natural substances that catalyze chemical reactions in living organisms. By removing moisture through freeze drying, we greatly reduce the water content needed for enzyme activity. This, in turn, slows down their function.

While freeze drying can slow down enzyme activity, it does not necessarily destroy them. However, some cooking methods, like blanching and adding chemicals, can destroy enzymes. To blanch foods, briefly put them in boiling water or steam. This process can destroy enzymes by changing their shape. When cooking, certain chemicals like enzyme inhibitors or ascorbic acid can destroy enzymes.

Does freeze drying destroy probiotics?

Probiotics are live microorganisms that provide numerous health benefits when consumed. These beneficial bacteria are extremely delicate and can be easily destroyed by heat, moisture, or oxygen. Freeze drying is a gentle way to preserve things by removing water without using high temperatures.

During the freeze-drying process, the food product is frozen and then placed in a vacuum chamber. Sublimation happens when the water in the product goes from frozen to gas without becoming liquid. Preserving probiotics is important, so we use this process to minimize damage from heat or moisture.

Can bacteria survive freeze-drying?

Yes, certain types of bacteria can survive the freeze-drying process. These are typically bacteria known for their strong spore shells, such as Bacillus and Clostridium. While the freeze-drying process generally kills off most bacteria, these resilient types can survive and potentially pose a risk if ingested.

Is Salmonella killed by freeze-drying?

While the freeze-drying process can kill many types of bacteria, Salmonella can sometimes survive, particularly if the food was contaminated prior to freeze-drying. This is due to Salmonella's ability to survive in dry conditions. It is essential to maintain good hygiene and proper handling procedures to minimize the risk of Salmonella contamination.

Can you get sick from freeze-dried food?

Yes, it's possible to get sick from freeze-dried food if it's contaminated by bacteria that survived the freeze-drying process or introduced during packaging or handling. Proper hygiene practices, careful packaging, and correct storage conditions are crucial to prevent any bacterial contamination and maintain the safety of freeze-dried foods.

Will freeze-drying kill mold?

Freeze-drying does not effectively kill mold; it merely dehydrates it. While the process can halt mold growth by removing the moisture it needs to thrive, any existing mold spores can become active again if introduced to favorable conditions. Therefore, it's essential to ensure foods are mold-free before freeze-drying.



Freeze-drying is a highly effective method of preserving food, extending its shelf life while maintaining much of its original texture, flavor, and nutritional value. However, it is crucial to remember that the process, while effective in killing many bacteria, is not entirely foolproof.

Issues such as bacterial composition and the type of food being freeze-dried can impact its effectiveness. Measures such as practicing good hand hygiene, preventing cross-contamination, and ensuring stable storage temperatures are vital to ensure the safety and longevity of freeze-dried products.

By adhering to these measures, we can enjoy the benefits of freeze-dried foods without compromising our health.


  1. National Center for Home Food Preservation. (2020). How Do I? Freeze. Link
  2. U.S. Food & Drug Administration. (2018). Safe Food Handling. Link

Last Updated: 05 December 2023


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