The Steps Involved in Freeze Drying
Freeze drying is also referred to as cryodesiccation or lyophilization. The process of freeze drying involves freezing a product, followed by lowering the pressure, then removing the ice on the product by sublimation. In short, freeze drying aims to remove water from any frozen product using sublimation. The process of freeze drying can be done at home or commercial. A commercial freeze dryer requires the use of commercial facilities, as well as large freeze-drying equipment.
Some of the common facilities commercial freeze drying is conducted in include:
In-house and large scale drying for one particular product like Coffee.
Small to moderate freeze drying that is used for the production of different freeze-dried ingredients that are required in the product composition companies make. For example, poultry, vegetable, meat, herbs, pasta, and condiments for dry soups.
Custom freeze-drying facilities that are dedicated to commercial freeze-drying for third parties.
Steps involved in the freeze drying process.
There are three steps involved when it comes to the freeze-drying process. The three steps include:
Freezing: The product is first cooled and then frozen throughout. Freezing the product commercially can be done either in a commercial freeze drier, a basic chest freezer, some types of freeze dryer, or specialized laboratory equipment that commercial facilities use for freezing. These freezers slowly freeze the product enabling it to create large interlinked crystals that help in facilitating the removal of vapor during the sublimation process.
The sublimation process then allows the products to freeze faster during the cycle. However, large interlinked ice crystals are not always required. The reason for this is because organic or food cell structures tend to rupture the plant’s cell walls and damage the entire end product. To prevent this from happening, commercial facilities, accelerate the freezing process of the product, and this creates ice crystals that are smaller in size.
The next step is the primary drying. In this phase, the chamber pressure is lowered, and the condenser starts to drop its operating temperature. Heat energy is then supplied to the product, and this begins the facilitation of the sublimation process. This process causes the product to dry from the outside inwards. Meaning that the thickness of the material determines the duration of this process.
The last phase of freeze drying involves the removal of unfrozen moisture that is not ice but has instead bound itself to the product. The moisture is removed through desorption, and the rate at which this happens depends on the temperature of the product. This stage requires an increase in the rate of absorption, and commercial facilities make sure that they do not damage the product with excessive heat. Once the secondary drying stage is complete, the product is finally ready.