Freeze Drying Food Process
Before we talking about the freeze drying food process, we shall first know how does a food freeze dryer work. Here is the detail.
How does a food freeze dryer work?
A food freeze dryer is a drying machine in which water-containing substances are pretreated, rapidly frozen at -30°C and in a vacuum environment so that the water in it is sublimated from a solid-state to a gaseous state to remove water but leave the substance.
The freeze-dried food processed by the qualified freeze dried food machine should be like this: the water content is 5% or less; the appearance is complete, basically does not shrink, and the product is very crisp, easily breaks when slightly pressed.
What is the freeze dried food process?
Freeze dried food process — pretreatment
General pretreatment refers to all treatments before sublimation drying, so freezing before drying also belongs to pretreatment. The pretreatment of raw materials requires selection, cleaning, peeling, cutting, blanching, cooling, etc.
Pre-freezing is to freeze the pre-processed raw materials. Since fruits and vegetables will undergo a series of complex biochemical and physical-chemical changes during the freezing process, the quality of pre-freezing will directly affect that of freeze-dried fruits and vegetables.
Freeze dried food process — sublimation and drying
It is the core process in the production of freeze-dried food, and the following process conditions must be controlled:
1) Loading capacity
The loading capacity of the lyophilization machine is an important factor in determining the drying time. The thickness of the dried food is also a factor that affects the drying time.
In the actual drying, the dried materials are cut into a uniform thickness of 15 ~ 30mm. The amounts of materials to be loaded should be determined according to the heating method and the types of dried food.
2) Drying temperature
In freeze-drying, in order to shorten the drying time, the heat required for the sublimation of ice crystals must be efficiently supplied. The drying temperature must be controlled so as not to cause the ice crystals to melt, nor the dried part has any thermal denaturation due to overheating.
Freeze dried food process — Post-processing
Post-processing includes unloading and semi-finished product sorting.
After the freeze-drying is completed, inject hydrogen or dry air into the drying chamber to break the vacuum, and then immediately remove the material in a closed environment with relative humidity below 50%, a temperature of 22 ~ 25 °C, and less dust.
Freeze dried food process — Packaging and storage
Freeze-dried food has a huge surface area. Some ingredients in the food are directly exposed to the air and are easily exposed to oxygen in the air and adsorb moisture, which will lead to its gradual deterioration. And most freeze-dried foods have natural colors, and these natural pigments are easily degraded under the light. In the process of oxidation and pigment degradation, the temperature is also an important factor affecting such chemical reactions. Therefore, the packaging of freeze-dried food mainly considers how to prevent or reduce the impact of the above factors.
How does a food freeze dryer work? And what is the freeze dried food process? Now you shall have the answer. Feel free to contact Hawach if you have any questions.