How Does A Freeze Dry Machine Work

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Over recent years, there has been growing attention around home freeze dryers. Their increasing popularity is largely due to their ability to totally dehydrate fresh and perishable foods. This process effectively prolongs the food’s shelf life and makes it much easier to transport. While the concept of home freeze drying is relatively new, commercial freeze dryers have been employed in the food industry for a considerable period. A home freeze dryer provides a simple and cost-effective solution for food preservation. Eating freeze-dried foods not only ensures you maintain nutrient intake but also preserves flavor. With a high-quality home freeze dryer, you can potentially reduce the drying time by up to 30%. To assist you in using a home freeze dryer and savoring fresh food throughout the year, we’ve prepared this comprehensive guide:

How to Use a Home Freeze Dryer

Also referred to as lyophilization in technical terms, a freeze-dryer essentially removes all the water from foods after being frozen and then places them in a vacuum. The process converts all ice into vapor by skipping the liquidation phase.

Freeze dryers work in three phases; first, they freeze the material, then reduce the pressure, and finally add heat to allow the frozen water in the material to vaporize, also referred to as sublimation.

Home freeze dryers work a lot like their corporate counterparts costing thousands of dollars. While the home freeze dryer is relatively new, its commercial counterparts have been around for a long time. However, commercial machines are bulky, hard to move, and certainly not worth spending money on to freeze three pounds of bananas. Fortunately, the latest freeze dryers available for home use are just as good, cost less, and are relatively easy to use on a small scale. If you have purchased one, below is how easy it is to freeze-dry just about anything.

Let us take a look at the process you need to follow when you are trying out your home freeze dryer for the first time:

Step 1: Start by placing what you want to freeze dry into the unit. 

Step 2: Hit the “Start” or “Go” button to start the process. Generally, the unit will start by dropping the temperature of everything inside to -50°F to freeze the food. 

Step 3: The vacuum pack will turn on, and that will begin pulling water out of the food. 

Step 4: The built-in humidity monitor will ensure that the water level in the food is the lowest it can possibly be. Then you need to finally shut the unit down when the food items have been completely dried. 

Even though each machine is designed differently, the main process is completely the same. You should ideally refer to the user manual of your machine to find out how exactly to operate the machine. Usually, it is as simple as pressing one button.

How Does A Freeze Dry Machine Work – In Detail

As mentioned earlier, a home freeze dryer works in three phases. Here we will discuss all three phases in detail.

The Freezing Phase

The freezing phase is the most critical phase of the entire process. The freeze dryer, based on which one you buy, can generally use one of the numerous methods available to freeze the product. Usually, the freezing steps work a lot like domestic freezers. The main difference here is that home freeze dryers are faster and get colder. Once the material is cold enough, when the sensors find out that it is cold enough, the vacuum of the machine will turn on. 

The freezing process is characterized by the appearance of ice crystals on food items. However, these crystals are usually small as if they are too large, they may break the cell walls, thereby reducing the efficiency of the product. Hence the freezing process needs to take place rapidly. 

The food items that precipitate will need annealing. This process usually requires fast freezing and then raises the temperature, which allows the crystals to grow. This will largely depend on what you’re freeze-drying.

The Sublimation or Drying Phase

Next comes the drying phase, also referred to as sublimation. In the sublimation phase, the pressure is lowered and heat is added for the water to quickly sublimate. The powerful vacuum present in the freeze dryers will help in shortening the time to sublimation. The cold condenser provides the surface with water vapor that can adhere to and solidify quickly. The condenser is also responsible for protecting the vacuum pump from vapor.

Most home freeze dryers can remove up to 95% of the water content from the material during the sublimation phase. Even though primary drying is a slow process, if too much heat is added, it will change the structure of the food material. Some food materials will be more affected than others. This is why sublimation is an automated process in most home freeze dryers, where some machines can do a better job than others.

The Secondary Drying or Absorption Phase

This is the final phase in the process, during which the machine moves the ionically bound water molecules. The temperature is raised higher than during the primary phase, leading to breaking the bonds between the material and water molecules. The resulting materials will be able to retain their porous structure.

Once the freeze-drying process is complete, the vacuum is broken with inert gas, before the material is sealed. Based on what you are freeze-drying, a home freeze dryer can dry material to around 1%-5% of moisture.

How to Store Freeze Dried Items

The best way to store freeze-dried fresh foods is by storing them in cans and mylar bags. However using can get quite expensive for a home user but if you are planning on doing this professionally, cans will be worth it. For home users, we can use mylar bags easily as they contain metal within the fabric that can keep the light out. Since you are going to be freeze-drying perishable food items, you need to be extremely careful when it comes to storage. With fresh foods and other consumables, you cannot run the risk of them going bad.

Some things to keep in mind when storing freeze-dried items

  • Avoid using clear plastic bags to store fresh foods as they may allow both water and oxygen to get in. Oxygen and water can cause rancidity in your food even if your bags are sealed. 
  • You can also use mason jars. The only downside with mason jars is that they are quite fragile, heavy, and can get a little expensive. If you go for a mason jar, make sure that after you fill the jars with your food items, you store them in a dark location. This will prevent freeze-dried food from getting into contact with light which can cause it to get discolored. 
  • If you are using a container to store freeze-dried foods, make sure that you put in an oxygen absorber to prolong its life. Once you seal the container, the oxygen absorber will be able to pull all the oxygen out from the bag. 
  • If you are using bags to store the food, you may also want to seal them using a heat sealer. You can opt for a hand sealer for home use.

Things to keep in mind while using your home freeze dryer

You need to keep a few things in mind when using a home freeze dryer:

  • You should change the oil in the home freeze dryer before every new batch you want to freeze dry. 
  • If you are using filtered oil, you want to double-check to ensure that no water gets into the pump. 
  • When you allow the filtered oil to sit for some time, the water and oil should separate. 
  • When the oil, as expected, starts to float on top of the water, then just pour off the oil to be reused and then discard all the water.

How Long Does Freeze-Dried Food Last

When products, particularly freeze-dried foods are said to have a long shelf life, it is an indication of how long these food products will be able to retain their original taste and nutrition. This is generally called the “best if used by shelf life.” You will be able to see this date mentioned on most food items available in grocery stores. Generally, it can vary from a few days to a week, depending on what you buy. 

Some products also have so-called “life-sustaining shelf life.” This number mainly indicates how much time the product will be able to sustain life before it starts to decay or becomes inedible. This could last anywhere from a few years to decades. Home freeze-dried items often last from 10-25 years. However, the key to the shelf life is the preservation process being used and the storage conditions of the food items.

Dehydrated vs Freeze-Dried Foods

A lot of people assume that freeze-dried products and dehydrated food are the same things. However even though both of them end up offering a pretty long storage life, their life-sustaining shelf life and their preservation process are very different. These characteristics make dehydrated and freeze-dried foods a great addition to emergency kits.

Here are a few differences between dehydrated foods and freeze-dried foods: 

Moisture: Freeze drying helps in removing up to 98% of all moisture from food items. However, dehydration can remove approximately 90% based on the food item. 

Shelf life: The amount of moisture present in the food item will typically affect its shelf life. Freeze-dried food with far less moisture can last for up to 30 years, whereas dehydrated products can last up to 20 years at max. 

Nutrition value: Freeze-dried foods aim to retain most of the original vitamins and minerals of their fresh counterparts. On the other hand, the dehydration process can often break down those nutrients, and make them comparatively less nutritious.

Can You Build A DIY Freeze Dryer

Building a freeze dryer is far from impossible. In fact, many people do it. However just because it is possible, does not always mean that it is the most viable solution to your freeze drying needs. Building a freeze dryer yourself is not necessarily the easiest DIY project in the world, but there is a lot of content available online that makes the process seem simpler than it actually is. Unless you are comfortable with building stuff, can get a hold of some exotic parts, and have in-depth knowledge of how gases work, with working knowledge of electronics attempting this project can be pointless. You might end up spending more on building a DIY freeze dryer than buying one.

Why is Freeze Drying Worth It

Many people may question if investing a lot of money in a freeze dryer and dozens of mylar bags are worth the time, money, and effort? Yes, it is worth the effort because it can literally save your life. As we’ve already established, freeze-dried products can last for years, and that means if there is a food shortage, famine, or war, you have a running supply of everything from chilies to onions, beans, and everything in between. You can cook using freeze-dried products, or in the case of fruit, chew on them to keep yourself alive. That being said, they don’t taste bad at all.

You can also use freeze-dried foods in times when prices for certain vegetables and fruits skyrocket. Also, you can enjoy fruits that are otherwise not available all year round. Freeze-dried foods are also perfect travel companions as you can just pop open a can and start cooking anywhere you like.

We often tell people that once you start freeze-drying foods, you will begin to wonder how you lived without them. It is, by far, the most efficient way to build up a stock of foods you like, which can be used in times of emergencies when there are floods, forest fires, or storms that leave you stranded.