ntroduction for Freeze drying technology:
Freeze-drying, also known as lyophilisation, or cryodesiccation, is a dehydration process typically used to preserve a perishable material or make the material more convenient for transport. Freeze-drying works by freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to the gas phase.
The freeze drying process is to freeze the materials firstly, and after frozen the products will be load into the vacuum drying tank which will bring the vacuum environment for the ice to sublimate to vapor, and with the condenser inside the tank condense the vapor to ice on the surface of the coils, the products will be dehydrated. Working principle of Freeze drying
The technology of Vacuum freeze drying is mainly utilizing the principle that water will sublimation directly from ice to vapor when it is in some specific vacuum environment. The freeze drying process is to freeze the materials firstly, and after frozen the products will be load into the vacuum drying tank which will bring the vacuum environment for the ice to sublimate to vapor, and with the condenser inside the tank condense the vapor to ice on the surface of the coils, the products will be dehydrated.Advantages of Freeze dried products:
There are several advantages of freeze-dried products when compared to regular hot air dried products.
1) The freeze dried products have long preservation time. If a freeze-dried substance is sealed to prevent the reabsorption of moisture, the substance may be stored at room temperature without refrigeration, and be protected against spoilage for many years. Preservation is possible because the greatly reduced water content inhibits the action of microorganisms and enzymes that would normally spoil or degrade the substance.
2) Easy transportation. With light weight and well packed freeze dried products can be easily transport by normal containers or any other transportation method. No needs for cold storage facilities therefore save a lot of cost for transportation.
3) Better quality products. Freeze drying causes less damage to the substance than other dehydration methods using higher temperatures. Freeze-drying does not usually cause shrinkage or toughening of the material being dried. In addition, appearance, flavors, smells and nutritional content generally remain unchanged, making the process popular for preserving high quality food.
4) Extremely high rehydration capacity. Freeze-dried products can be rehydrated (reconstituted) much more quickly and easily because the process leaves microscopic pores. The pores are created by the ice crystals that sublimate, leaving gaps or pores in their place. This is especially important when it comes to instant or convenient food uses. Main components of freeze drying system:
> FD drying system (FD drying tank)
> Heating system
> Cold trap condensing and defrosting system
> Vacuum system
> Freezing system (freezer)
> Refrigeration system
> Material handling system
> Control systemPictures of Vacuum freeze dryer