Freeze dryer

Freeze drying is a method that takes the water out of a product while keeping its structure and nutrients. It makes things last longer than other ways of keeping them fresh. The machine used for this is called a freeze dryer, and it's often used for food, medicine, biological samples, and other things that can spoil.

How does a freeze dryer work?

In simple terms, freeze dryer machines work in three main steps. The first one is freezing. Quickly freezing the product super cold, way below zero, is key to making tiny ice crystals. This fast freezing also keeps the cells and material whole, making sure things like texture and shape stay the same during the freeze-drying process. The second step is called primary drying or sublimation. During this phase, the pressure is reduced, and heat is added to the material to make the water turn into vapor directly. About 95% of the water in the material is removed in this phase. The final phase is secondary drying (adsorption or desorption). After the primary drying stage, there may still be residual moisture remaining in the product. Heating it up more than in the primary drying step breaks the links between the material and the water molecules inside it. This additional heat helps evaporate the remaining water molecules, ensuring the product can be dried to 1-5% residual moisture.

Types of freeze dryers

There are food freeze dryers, whether it is to make military food, dairy products or dehydrated food. In addition, there are various teams applied for the pharmaceutical sector, towards the conservation of vaccines and medicines. Similarly, there are freeze dryers that are used in the performance of water-damaged documents. These are grouped by size into laboratory units, for the progress and increase of processes and devices of larger production size. Another way to tell the difference between types of freeze dryers is if it's for use at home or for a business. A big difference between a home freeze dryer and a commercial freeze dryer is how much it can hold. Home freeze dryer capacity is less than 5kgs. Commercial units can be tons. For sure, products dried by commercial freeze dryers have better quality. The reason is simple: commercial units can precisely control the sublimation temperature and vacuum pressure, which potentially influences the freeze-dried product quality. And last, professional commercial freeze dryers' prices are times higher than home units.

The difference between a freeze dryer and a dehydrator

People often talk about freeze dryers vs dehydrators when deciding how to keep food fresh. Both keep food good for longer, but they do it differently, and the results are different, too. Freeze dryers freeze the food, then lower the pressure and add heat so the frozen water in the food can turn directly into vapor. A dehydrator dries out food with air at low temperatures. This lower heat level means that the food does not cook in the machine. When it comes to how long freeze-dried food and dehydrated food can last, the freeze-drying method takes out almost all the moisture (up to 99%), which helps preserve the food for 25 years or even longer. On the other hand, dehydration only removes around 85 to 95% moisture, so dehydrated food typically lasts for a few months to a year.