Does Freeze Drying Kill Bacteria?

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Freeze-drying food is constantly evolving. When before, it was done in large laboratories and food factories, now you can do it at home. It’s gaining popularity because it is one of the safest and healthiest methods of food preservation. But does freeze drying kill bacteria?

Not Entirely

Freeze drying or lyophilization is the process of removing up to 97% of water from food. Bacteria have been known to lay dormant for thousands of years and come alive once exposed to ideal conditions.

It’s the same with the process of freeze drying. Because the process of freeze drying is to:

  • Protect perishable materials
  • Extend shelf life
  • Provide convenience for transport.

So when you expose bacteria in the freeze-drying process, it’s the same thing. Their DNA doesn’t come apart. Why? Because the surrounding cellular material protects it. Some do experience freezer injury when exposed to slow freezing. Ice crystals form, and their sharp edges can damage bacterial cell structures and wall membranes. The change in pH also causes harmful effects on their biological functions.

Some yield to this injury and die. Others go into survival mode and start to become dormant. But once you expose them to heat and water, they come to life and begin to multiply.

What Bacteria Reacts to Freeze Drying?

Does freeze drying kill bacteria? Not in entirety. There are so many bacteria and pathogens found in raw food that react differently.

Let’s take raw meat, for example. What most research found is that it kills a percentage of bacteria. Only a percentage because most of the bacteria present in raw meat are

  • E. coli
  • Yersinia
  • Campylobacter
  • Salmonella

bacteria present in the kitchen and food

These bacteria are gram-negative and have cell membranes resistant to freeze-drying. Remember when we talked about removing grapefruit seeds because they have a thick membrane? It’s the same with gram-negative bacteria.

Campylobacter, for example, showed high sensitivity to freezing drying. So, you can effectively reduce their numbers just by freezing them. But some still remain. For E. coli, half of the population present remains in the food.

For Salmonella, freeze-drying makes them go dormant. They stop multiplying but can still persist in your freeze-dried products. The numbers are lesser compared to dehydrated food, but they’re still there, nonetheless.

Factors Affect Bacterial Response to Freeze Drying

Several factors influence the bacterial kill rate. These are:

  • Fatty tissue – fat creates a protective layer around the bacteria that protects it from the damaging effects of freeze drying.
  • Location – bacteria found on the surface get affected easier by the freeze-drying process. Those found in the middle aren’t easy to target and can have lesser damage.
  • Nature of bacteria – spore-forming bacteria are tougher compared to those who don’t.

How Can I Reduce the Number Of bacteria?

The best way to reduce bacteria is to observe strict sanitary practices in your food. Even if there are measures done to lessen bacteria, contamination can still happen at home. Here are ways for you to lessen bacteria exposure in your freeze-dried food.

Practice Handwashing

Our hands touch virtually almost every surface on the planet. That’s why food handling is the main source of food contamination. Your hands can spread:

  • Dirt
  • Trace amounts of fecal matter
  • Bacteria and viruses from infectious diseases

Practice strict handwashing when your freeze drying food. Scrub your hands with soap for 20 seconds. Sing “Happy Birthday” twice or the alphabet once before rinsing off.

hand washing to prevent cross contatimation

Prevent Cross Contamination

Surfaces can harbor bacteria when the come in contact with raw food. Especially when you’re handling meat and poultry. Cross-contamination can happen when you use the same knife, chopping board, or other utensils without washing them well.

Always wash the trays you will use, and keep the surfaces clean. Use disinfectants to sanitize counters, sinks, and tabletops before and after each use.

Keep A Stable Storage Temperature

Every time we talk about storing freeze-dried food, we always stress on the room storage temperature. This is because not only does it degrade food nutrients, but it also encourages bacterial growth.

Your food storage room should be at a stable temperature and not go above 72°F (22 °C). Any higher than that would result in microbial growth and the multiplication of pathogens.

Does Freeze Drying Kill Bacteria?

To a certain extent, yes. Unfortunately, some bacteria are still made of strong stock and go dormant. Once exposed to heat and water, they come alive and start contaminating your food.

Research shows gram-negative, and spore-forming bacteria are least likely to succumb to freeze drying. Also, the amount of fat and how deep the bacteria’s positioned can lessen the effects of freeze-drying.

The best way to fight bacteria is to lessen the food’s exposure to it. Practice proper food sanitation as if you’re processing food in a food plant or professional kitchen. Think that you’ll get sued by powerful billionaires when they get food poisoning.

After processing, it’s important that you store them properly. First, keep a tight seal on your Mylar bags or mason jars. Then do your best to maintain a storage temperature of less than above 72°F (22 °C). Even a single degree increase can make a huge difference in your freeze dried food supply.

Hope we answered your question about does freeze drying kill bacteria. If you have more questions or would like to share your point of view, please do so in the comment section.

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